What's the law on hit and run?

Whenever, you are involved in any sort of vehicular accident (the "hit" part), those involved are to stop and exchange information. Failure to do so, is the "run" part. By "running" you are aggravating a situation that would otherwise be minor. If you were the one who did the "hitting" you need to stop. If the other person fails to stop, then there is no much you can do about that. If the other person did the "hitting" and "running" and you cannot get him/her to stop, then report the matter to your carrier if the damage is more than you want to pay out of pocket (usually it should be more than your deductible). Try to get the license number of the vehicle that hit you. You can then file the claim on a DMV form (SR-10, I believe) and report it to the DMV which will take appropriate action against the offending vehicle, but it needs the license number of the car to do so.

It is illegal to flee the scene of an accident.