The problem with a number of fish today is tumors. Tetras do not have that fleshy forehead so it may be the beginnings of a tumor or it could be in internal worm making it's way out of the fish's body. At this point, there is nothing you can do past placing this fish in a separate hospital tank so that should it be a worm, you will see it on the tank bottom when it leaves the fish. If it's the beginnings of a tumor, there is nothing you can do for the fish. As long as it's eating, it has a chance to live with the tumor. If it stops eating, it would be best to euthanize the fish because the tumor is obvious in position that may be effecting the fish's brain. Head worms and tumors on a small fish are always hard because there is such little room for growth without effecting more vital areas.Hi! This is on one of my glofish. None of the other fish have this, and all (including this guy) are swimming and eating normal. Should I be concerned?