Depends. Check the manual. Britax follows NHTSA guidelines for minor crashes. Most brands declare that a seat must be replaced after any crash and they don't define crash. If there was damage to the vehicle, I'd replace the seat if it's a brand which declares as such. Insurance should cover it, but it may take some firm Mommy voice.

There's no way to visually inspect a carseat to see if it has been damaged. The cover can be salvaged from a beloved seat and put on the same model. (Also, most folks don't realize that *seatbelts* also need to be inspected and potentially replaced.)

http://www.car-safety.org/faq.html#Q27
http://www.nhtsa.gov/people/injury/childps/ChildRestraints/ReUse/RestraintReUse.htm (not loading for me right now)