Gave my number to a stranger. What do I do?

Well short of getting a new number (usually far too drastic even to consider) just learn from the experience and be careful who you give your number to in future.

That also applies to giving out your email address. Don't be in too much of a hurry to put that on web sites where it will be passed around to spammers. You need a second email address you only use when it's necessary to register on a site and whose incoming messages you can safely ignore. (Or a temporary address provider like www.spamgourmet.com which will delete all incoming emails after a period you specify.)

To think that you had enough common sense to prevent such a thing.

I mean, nothing unless something comes up.

Unless the person starts harassing you, you live and learn. If they start harassing you, you document it and turn it over to the cops.