Difficult to tell from your photos, but it appears to me that it may be lymphocystis. Lymphocystis is a virus that is somewhat analogous to herpes in humans. It is thought to be caused by stress. Viruses can lead to secondary infection, which can be medicated for, but the virus itself is untreatable. The good news is, that the virus can go into remission if the fish is otherwise healthy and stress-free. Lymphocystis is contagious to other fish, particularly other fish in the same species. Lymphocystis enters the fish's system via minor injuries. It is not contagious to humans.
Keep in mind, this information is only valid if it is indeed lymphocystis. I cannot tell with any certainty from your photos. Lymphocystis tends to look much like cauliflower, especially as it advances.