Honestly, it depends. If he were to press charges and you were found guilty of assault, then you likely would have to pay restitution. If it comes out that you were defending yourself from this assailant and the damages resulted from that, you probably will not have to pay damages.
Defending yourself from an attack could justify your doing damage to the car but it really depends on the situation. Also while you may be protected from criminal prosecution due to the self defense doctrine that does not necessarily prevent the police from charging you ( you may end up with a "he said/she said" situation nor does it insulate you from a civil suit for damages. Remember being charged or sued in the civil world is different from being found guilty or liable in a civil suit. Consult with an attorney and don't discuss the case with anyone but your counsel.
This information does not create an attorney /client relationship and should not be use or relied upon to make any decision in your case. Only consultation with your own attorney can provide you with the advice you need for your case.