Advice for a small traffic accident

In this weekend I did a stupid thing. In a parking lot, when I backed my new car, I accidently hit another vehicle front driver-side door. I left the scene in a hurry ( somebody has witnessed the accident, wrote my license number). I went to another shopping mall and realized that actually my car got much more damage than the hit car. I went back the scene, the car has gone. In the evening, I called the insurance company describing the accident.

I wondered if I need to report case the police also to avoid some lawsuit. What else can I do?

thanks
_:'( _:$