BLUE TONGUE SKINKS

Hi,
I got my first northern blue tongue skink Thorin, back in April he's about 4 months old, a couple weeks ago there seem to be a scratch or something eating at his scales on his back I did some research thinking it was mites, but from my understanding you can see mites on your animal and I have never seen any on him at all. So I figured I would post the pictures here and see if anyone knows what's happening here!
Thanks!

I do not see anything to be concerned about there, sometimes they just do things to themselves causing an odd scale here and there. Mites on captive bred animals are rare. Often seen on newly imported animals or that from a pet shop or expo.
See if it resolves itself next shed.