This kind of thing is too big to have secret in a relationship. It's something you need to talk to him about and try to get over. This kind of thing is not something that stays a secret either. Even little things get around, and people you hardly even know may even know what happened by now. It's best to for him to hear it from you, because chances are he'll eventually hear it from somebody else. But he does deserve to know, it's not fair to him if he doesn't. He should also know so that he can re-evaluate his friendship with the other person.
If your honest and up-front with him you can work through things. Perhaps you can even offer to go to counsiling with him. But whatever you do don't play the blame game, take responsibility for what you did wrong.
