If your B/F gave him a black eye it means he must really care about you as I know a lot of guys who would just laugh along and not risk falling out with their mate.
Ideally, your B/F's friends and you would all get on, but in reality this happens to a lot of couples. I see a lot less of my mates now as they have settled down, as have I. But, you have to grow up and accept that you people move on and find hapiness with others. It is usually the ones who try and pull the girls and do not want to settle down that ultimately end up alone with nobody to love.