Picture is blury, but if those are holes in the center of the lesion, I'd guess a parasite like a fluke (like yellow grub). The spacing seems peculiarly regular. Haven't seen anything quite like that before.
It'll either run it's course, succumb to treatment, or the fish will. Might consider trying a net dip using a heroic dose of malachite green if all else fails. But that really is an option of last resort.