Hello,
That looks somewhat like retained shed to me. How long has this been present?
Does it seem to be bothering him?
You could try soaking a soft toothbrush in warm water & gently scrub that area to see if the
scale works off.
It does have a little reddish speck but I don't think it appears to be an injury on there though.
If you have some raw unpasteurized or manuka honey you could put some of that on there,
too.
Tracie