Take picture on the spot with your phone and measure the height of the door corner to the dent of your door. He can't deny.
There was a time I was sleeping in the back seat of my dad's car while my parents went into T&T, then I heard and felt something hit the car. I woke up and saw it's the door of the car next to us. After I got out of the car and talked to this mainlander, he offered to give me $5 to the chipped paint on the door handle. But $5 is not enough to buy the paint pen from the dealer and his attitude wasn't apologetic at all, so I took his driver license and insurance and report to ICBC to repair it just to teach him to be careful and understand his wrongdoing.
The final cost was like $300 something and the trouble for us to get it repaired. If he was apologetic and offered to pay $20 then we both don't have to suffer.
You just have to be prepared to call police is he runs away. Always take a picture of the license plate before the talk, and it's a good idea to have at least one auto upload photo service (dropbox, google+, or facebook) on your phone so that if he grabs your phone and destroy, you can still have record.