Nothing to worry about. Salt it down to make sure the "craters" aren't infected. I have had problems like this in peacocks and from my experience they were genetic mutations. HITH disease would show signs of lateral sunken lines, especially at the head or temple, so I doubt that is what this is. If you look closely at fry you can see craters on their heads also. You have nothing to worry about as they could have been caused by another fish fighting with him, coral being imbedded in his face, and so on...