That's what I figured, I k kw they are prone to HITH but I don't think that's it? Hard to get a good picture.. he comes to me when I walk by the tank but as soon as I put my phone near the tank he hides lol
Looks like a scratch from hitting a rock. Nothing major, no need to worry. Simply just keep your water clean by doing water changes and add some kosher salt to the aquarium.