If someone sins against us, we are to rebuke him. We know from elsewhere we are NOT to hold bitterness; if we do that, we should pray that our bitterness be released immediately and let God replace our bitterness with something else, and joy would be a nice replacement in this situation.
We state the facts of what he did, we tell him he is wrong, we tell him what he should to do make it right…If he sins against us 7 times, we are to rebuke him 7 times.
We are to forgive him completely if he repents (Jesus' words). That mirror's the way God forgives - if we repent, He separates our sin as far as the east is from the west.