Infidelity Support Group
Any relationship in which one partner engages willfully in sexual relations with another outside of the partnership is considered to have experienced infidelity. This breach of trust is often traumatizing for the faithful partner as well as the relationship, and support is often needed to heal emotionally and to decide whether or not the relationship should continue after...
As long as you are fully honest and open with your bf, that is all you can do. Be sure to confess ANY guilty feelings and the rest is up to him. If you cannot wait it out, try a short separation (to preserve your heart) but give him the time he needs to get through whatever the missunderstanding is.
I agree with Johna. If my partner stayed in contact with a friend who had acted inappropriately I would feel very uncomfortable with that. Perhaps that is why your partner suspects more and doesnt trust you.
Other than cutting ties with the friend, if your partner cant move on from this after a long while then perhaps the relationship will have to end. It may take a few months or so for him to be able to trust you tho. I dont know how long ago this happened but give it a reasonable amount of time. If your friend has remorse for what he did maybe have him chat to your partner on the phone to explain that he was the one who kissed you and it was not your doing. all the best