What kind of relationship do you have with your boyfriend? Are you going to be screwing around with other guys while you are with him? Are you going to be faithful from now on? Is he faithful to you? How is he going to react when you tell him you had sex with someone else? If you are both in a monogamous relationship, I am sure he will probably be very angry when you tell him you slept with someone else. He may be so angry, in fact, that he may never want to see you again.

So it's really up to you. If you learned your lesson and will never do it again, you may want to keep it to yourself, but will you be able to continue your relationship without feeling guilty? Only you know how you are going to feel and how your boyfriend will react. Sometimes, a mistake can teach us a lot of things about ourselves and about our relationships. Unfortunately, there is always a price to pay. Good luck!