Not only can this behavior cause damage and scarring to the mouth but also may dislocate the jaw itself. First I would separate these two males. These fish will continue fight until one is eventually killed. In the wild the subdominate male can swim on to a different area in the lake, but in our aquariums the battered have no place to go. Altolamprologus compressiceps normally breed one on one or in trios, so by putting all the rejects in a separate tank allows them to also naturally pair off.
Fish are amazing in the way they can heal themselves especially when they are healthy specimens.
It is important that your water is clean to insure that no disease or infection will set in. If the sore becomes infected it is probably because of poor water conditions, this is where bacteria can be found. Remember preventative maintenance, this means regular in consistant water changes, is the best cure against any diseases, it is essential that you keep your water conditions in top form. So separate the fish and do a regular water changes.