It sure sounds like “hole-in-the-head” disease.Oscars are particularly susceptible to it.It’s usually caused by poor water conditions,that compromise the fish’s auto-immune system. The treatment is to get the water into good shape and keep it that way with weekly 25% water changes. If you get the water clean it will slowly heal.—–Good luck.—-PeeTee— The disease can also show up as lateral line erosion,or holes along the lateral line.