Don't take anything for the car damages until you have a repair facility actually look at the damages and give you a repair estimate.
This answer is offered for informational purposes only. It is not offered as, and does not constitute, legal advice. Laws vary widely from state to state. You should rely only on the advice given to you during a personal consultation by a local attorney who is thoroughly familiar with state laws and the area of practice in which your concern lies.
It sound like a minor impact case. You should probably have your car inspected to determine the full amount of damages and then work with the other driver's insurance company to get it fixed. If you were not injured, you probably don't need an attorney.
You will wantto make sure you take it to a repair facility and get it checked out before you accept anything from him. I would also not sign a release until you had it reviewed by a lawyer!
Get yourself a repair estimate from a reputable shop. Tell them that you specifically want them to inspect for under-body damage. If none is found, and you were not injured in the accident, settle for the cost of the repairs if you like. If you were injured, or if there is more damage than meets the eye, seek the advice of a personal injury attorney immediately.
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