Well I don't know if it is the same for med school, but I know when I went to law school you were supposed to disclose any arrests etc you had and then I had to fill out a moral character application for the State Bar to give me a license. If you did not disclose any of your arrests etc in your law school application you could it was possibly for them to deny you a license for dishonesty. The rule in the law is that when your in doubt disclose. I imagine your state's medical board would have a similar licensing procedure, but I don't know. I would contact the medical licensing board from your state and ask anonymously what you need to do.
As Foster suggested this is probably not the best place to get information for something like this. In the law it is when it doubt disclose not sure about medical school, but ask the licensing board or something else. Furthermore, this doesn't sound like a major incident you were 17 and stupid as many people are. If you come forward and say you learned your lesson there is a good chance they will forgive you, but if you try to hide the incident you have now become a liar right now and have this criminal record. Often you disclose minor incidents people are forgiving, but if you lie about one thing the question becomes what else are they hiding.

