Accidentally backed into UPS truck?

2 days ago, I went to back out of my driveway, and there was a UPS vehicle half in the road, half in the back of the store. I accidentally bumped into the back of his truck (softly because i was just backing out) and i absolutely panicked (because im 18 and just got my license in august) and drove up the small hill by my house and parked. I walked down the hill to talk to him and he was already driving away. he didnt take pictures to my knowledge or call the police. There are a few scratches on the back of my car, but thats from my step father backing it into cement on saturday. What's going to happen?