Dashboard lighting dims and then brightens on my mini cooper 2007. should i worry

Probably, but for the exact function of dashboard warning lights read the vehicle handbook or check with a dealer.

is it adjusted by the light switch left on bright right dim all when lights are on all dash lights will dim thats normal

Do you have a dimmer for interior lamps? Like a rheostat, a little wheel that you turn up or down to brighten or dim interior lamps. Usually the instrument cluster lamps brighten and dim the same way.
Can you brighten and dim the other interior lamps?

On your dash is a little round switch with a ballast resistor in it, by turning it clock wise or counter clock wise you can change the settings and intensity of your dash lights.

Need more detail.....

You don't say if it's "just" the dash lights, or if other lights do it as well. Try turning on a dome light and see if the dome light does it along with the dash lights. Do you notice your headlights doing this as well? These are just troubleshooting steps. If multiple light sources (dome, headlight, etc.) do it, then it's most likely a voltage regulator issue.

most dash lights you can brighten or dim by the light switch.

could be needing replace best to check with the main dealer

That should be your handbrake light

My 55 reg mini did exactly the same thing. I would not worry about it. You should still be within your TLC warranty period anyway? No?