It appears you were stopped and cited for a hit and run or leaving the scene of an accident. In most states this is a serious offense. It will depend on what state you live in as to the penalties that might be issued to you. In all states you are likely to be held responsible for any damages you caused to the other person's car that you hit.
In California, a hit and run is considered a misdemeanor and can be punishable by up to one year in jail and/or fines of up to $1000 plus expensive court costs. The penalites are even harsher in most states if anyone is injuried. In Wisconsin fleeing the scene of an accident that includes injuries can carry a fine up to $10,000 and a prision term of 42 months.
There are also likely points to be assessed to your driving record. In Pennsylvania it is 4 points, plus other penalties, for leaving the scene of an accident with property damage only.You should check with your state's Department of Motor Vehicles to find out what specific penalties the court might hand down to you.