Bottling up your feelings is never the answer. Let the anger flow. Feeling its harmful rays resonate within you is never the answer. Let the grudges flow.
The question is – how do you let it flow? You open up the cap of the bottle. Let it loose. Let what is inside come out. Talk about it, express yourself. Who knows! Maybe the insight you receive can free you from whatever kept your prisoner.
Talk to someone wise who understands you. If you are lucky, the person you have a grudge with can understand you, then you are as good as free from your bondage of anger.