If it were a near miss, then indeed just leave it and move on with your life, but if there's contact you should report it really. In this day and age everybody wants to sue each other. If he finds a scratch on his car later and changes his mind, deciding that you're to blame then you want to make sure your covered really. It probably won't happen, but some people can be incredibly unreasonable especially when a friend/relative/lawyer starts telling him how much it'll cost him to have a crack at getting some money out of you regardless of the circumstances.
If you choose to report it, you can tell the police that you don't wish to take any action at this time. You just fill out a pretty standard form and that'll be the end of it, but at least you'll have something to send back if a solicitors letter drops through the door one day.
I know it's a bit sad you have to consider these things nowadays and that you should be able to take someone on their word, but that's the world we live in....
Edit: and also, if you find later on that actually you might have been ok, but your forks have a massive crack in them and are now unsafe, then you're in a position where you can claim the cost of repair if you need to (without wishing to imply that you should jump on the compensation bandwagon). You'll have difficulty doing that if you haven't reported it.
