My handwheel is now stuck, nothing moves after I wound my bobbin...

I do not know the Husqvarna Viking 630. However, I have used the Viking 6690 and it has a similar on-the-side bobbin winding routine. I suspect that you failed to move the bobbin winding mechanism back into the sewing position. Look closely at the area around the bobbin winding spindle. It looks like there is a lever below the spindle. Does this need to be moved or rotated? Double check the steps in the manual and check that you did the opposite steps of preparing to wind the bobbin.

On the 6690, you pull out a knob after removing the bobbin. (You push this piece in and put the bobbin onto the now exposed spindle for winding.)

I hope this helps.

Cindy Wells

The bobbin winder tires on most of the new lower to medium end brother machines have a tendency to sort of melt. I honestly don't know what causes it, but basically the rubber ring that rides the handwheel and causes the bobbin winder to turn will liquify and drip off the bobbin winder and then re-solidify. It would be best to take your machine to a repair shop, to get the tire replaced and to have the old tire sludge cleaned out, though if you are adventurous, you could try it yourself. You can order a tire at the link I've provided, but most sewing machine repair shops can get you one as well.
Bobbin Winder Tire Babylock Brother X55238051

Cut the thread above the needle eye and rock the handwheel back and forth sharply to cut the thread with the sewing hook. If that doesn't work pretty promptly, undo the needle clamp and turn the handwheel, which should raise the needle bar. Then get into the bobbin case area and try to remove the bobbin case, cutting any threads you can. Keep rocking the handwheel and trying to pull out the needle (pliers help!), and eventually everything will loosen up.

Next, clean and lubricate the area under the needle plate and the shuttle, and reassemble. Put in a brand new needle, right way around and fully up in the machine. Load the bobbin case with a well-wound bobbin, and rethread the top of the machine and you should be good to go.

The bobbin might have a bunch of thread off it inside the compartment here the bobbin is. Also, make sure it's thread correctly, that can goof things up to.

most likely the bobbin thread is wound around the components.
remove the bobbin and check for a mass of thread cut it all away and remove every last bit then it should work

Take it back. New Singers are known for having problems. Upgrade to a Babylock.

Totally unwind the bobbin by hand to loosen it, even a couple of drops of oil wont hurt, you wound it too tight. Next time, slow down.

needle's in backwards

well!I If you buy a new sewing machine it has a manual to guide you in any brand.But if buy a used one sometime it doesn't have a manual, you didn't mention the type of sewing machine you want to use any how if you have a mechanical sewing machine it's better to start on it.First you must know and must familiarize the significant part of machine and important usage of them,I'll just mention the most usage part at start.Putting thread in bobbins first there is bobbins winder where thread was wind,draw thread from spool through bobbins winder tension disc located at top of machine.wind thread around an empty bobbins serveral times then,place bobins onto bobbins winder shaft with thread wound on bobbins clockwise sometimes this is located at top right side a shaft coupled to circular rubber touching handwheel perpendicular sometime it was located at right side front of machine near handwheel.Release clutch by pulling handwheelor rotating pivot wheel counterclockwise at the center of handwheel whlle holding freeze the handwheel tigh in order to disingage the motion of handwheel from mechanism of machine.

Can you post a photo of the machine, cannot find a reference to this model.

1st just check around the bobbin case area for jammed thread, also in/around the *takeup lever (up/down arm) mechanism near needlebar, as thread often gets wound around and jams the shaft

If it really seems like corrosion in an elderly & neglected machine.... disconnect from power, and using a small rocking movement of the handwheel to identify the parts that should move and with all the covers removed and in a dry well ventilated area with old newspaper to absorb excess,

.......give a light spray of WD40 or similar penetraing lubricant on horizontal Top shaft at each end where it joins main body

..... the region that operates the *take up lever cranks and counterbalance

.....the handwheel has a clutch mechanism, so if you can undo the wheel to access this, it may well be dry and need lube.

.....In the base is another horizontal shaft lube each end and a little where the gears meet to change the drive direction under the hook race/bobbin.

With the same gentle rocking motion of handwheel, see if there is any improvement ...but do not force anything......(to stitch forward, the handwheel spins "over the falls" toward you)

You may not see immediate improvement, so leave overnight and be patient, it may take several days........just be very sure there is nothing jammed anywhere.