I just noticed this yesterday when I was cleaning his cage. It's recent because I had just checked on him two days before that.

I'm not too worried about the actual cut because it's small, and I can get him to a vet if necessary. The issue is that he's had a cut before, not in the exact same place but near the same area. He's also missing some scales around the injury. So I'm assuming he's rubbing his nose on something in the cage. I've checked all of the plants for any sharp bits, and the screen of the Exoterra. Only other rough surface in the cage is his cork bark, but the first cut appeared weeks before I put that in (but I've also checked it for sharp pieces).

So the only thing I can think of is that he's rubbing his nose on the screen, but I can't think of any ways to get him to stop if that's the case. Any ideas?
(Sorry for poor quality, I will try to get a better picture tonight if anyone wants to see a closer picture)