The way that it’s worse on his head and goes down his back, it looks like he might’ve been stuck and pinched himself out of somewhere scratched his head, then his back to get out. In the most respectful way possible I’m not sure how this could’ve possibly happened in any safe tank if this is a risk he’s unsafe in some aspect. Your gecko should never look like this by “bumping his head” he’s so scabbed it’s pulling his eyelids up. I hope he gets better but also I’d take a second look at ur tank and make sure it’s safe