You can do this for now so its not driving you crazy, then get it fixed.
If your car horn starts blaring and seems to be "stuck" (it won't stop blowing), you could be in for a few embarrassing moments. There's nothing quite like the stares and expressive hand gestures you can draw as your horn takes on a life of its own. There are a couple of things you can do to get the horn to stop.
If it got stuck when you pressed on the horn switch on the steering wheel, it could be because the switch itself is stuck. Press the horn switch again, or tap it a few times to see if it gets unstuck.
Turn off the engine and look for your fuse box. Look through the circuit descriptions and see if you can find one for the horn. If you can, pull the fuse. This should silence the horn immediately.
If you can't find the fuse box, can't remove the fuse, or the horn doesn't turn off, then you need to resort to more drastic measures. Open the hood of the car and try to locate the horn. If the rear of the horn is visible, you might be able to see the wires that lead to it. Disconnect the wires. If you can't disconnect them, then cut one of the wires. If you cut the wire, wrap the resulting two ends of the wire with tape so that they can't short out your electrical system.
You could disconnect the main wires that run to your battery. You shouldn't cut these but should disconnect them using a wrench
. This might "reset" the horn. Hook the wires back up and if the horn doesn't turn back on, you should go directly to an auto repair shop to figure out what is going on. If the horn does turn back on, you'll need to locate and disconnect (or cut) the wires to the horn as previously described. Then, go to the auto repair shop and let them replace the horn for you.