Help!!!!

[Eyegore]

I hope everyones having a good monday. Well here's my problem, my headlights are on are bright (all 4) and when I hit the dimmer no lights except parking and running lights. All four headlights go completely out. The brake and tailights seem ok. So is it a switch, short or ??? Anyone else have a problem like this. My son did bump someone two months ago, strong enough to bend the bumper, but I never noticed the problem until tonight.

Thank you

Tom