Feeling unforgiven by someone can be very unpleasant. Your mind may go over and the situation with that person, trying to figure out what your part was or if it was even your fault. None of this changes the situation . But it can lead to ruminating about the situation and that can affect your mood and sense of self-esteem.
Here are ways to change the situation:
1) Have you asked for forgiveness with no blame or analysis added into it? This is the first and most important step. Even if you think you did nothing, have you quietly listened to why they feel the way they do then asked for forgiveness? If you have done so and they still don’t forgive you, then:
2) Are you respectful and kind to the person when you need to deal with them? This may help the other person to start trusting you again.
3) Don't keep apologizing. This will just make them less apt to forgive you. Apologizing sincerely and only once is enough. No one wants to feel coerced into forgiveness by the person they feel harmed them. Time and space may be necessary for forgiveness.
4) Some people need to hold onto resentments for some reason that you may never know and that has little or nothing to do with you. You can't do a thing with this type of person except treat them with courtesy and hope someday they come around.
5) What are the lessons of being unforgiven? Patience, self control, better boundaries, new relationships? How do these lessons make you a better person? If they never forgive you, but you as a result are a better person, then they have given you a great gift.
6) If nothing works, let go of them, and forgive yourself. You are worth that.