Many people may disagree, but forgiveness is OK. You are allowed to forgive. People screw up and make mistakes. We're human it's what we do. Just because people do bad things doesn't make them a bad person and if you say you've never done anything bad, you're lying. Forgiveness must be earned but should be given if you feel that it is right.
You can forgive but never forget.
Odds are the person you are forgiving has screwed up in the past. If this is the case and you are OK with forgiving them, then you must not forget what they have done to you. If they made you feel bad, then don't forget that. If they have lied, don't get that. Know that this can occur again. Odds are the person hasn't changed. People don't change, only the names do. I know that sounds incredibly cynical. When people hit a certain age though, that's normally who they are. You cannot change people, no matter how much you want to or how much you love them.
Forgiving people is OK. Don't forget what they have put you through.
In order to move on, you have to forgive or that'll eat at you. If you chose to never associate with that person again, that is also OK. You can forgive them in silence and without letting them know. Just forgive and move on. You won't forget and that's OK. Move on for you, not for them. You can't control what others do but you can always make the best of the situation. Just don't give people forgiveness who are unworthy of it. Don't forget that. We all deserve forgiveness, just make sure this person is worthy of it.