The past is the past. Whoever was at fault doesn't matter at this time. In the here and now, all you know is that you and another are in a state of hostility. At this point, there are two things you can do. You can let it go, and let it rot until one of you makes a move, or you can deal with the problem and fix things. It doesn't matter who was at fault, because that's in the past. The only thing you need to do is make things right. Don't rekindle the fire, and you don't have to apologize, but settle things, because the world has enough negativity as it is. Don't go to your grave with animosity in your heart.