If you truly believe that you had the best of intentions, and you did indeed "stop" the kiss from proceeding, then I don't think it's a problem to keep things from getting messy. You are young and still in school, which is a time when that sort of behavior is excusable.
On the other hand, if you believe that you made a mistake and the girl deserves better, then you should probably let her know. Some things are better when kept secret.







