What is this on my pythons tail?

[Dano94]

Looks like it could be stuck shed or a poorly healed burn. (Im no expert though!)

He hasn't shed for 3 months because he went off eating over the winter (He's back eating reguarly now though).

I was told by a pet shop that it could be a burn. Maybe he burnt himself on the heat mat in there? It is covered by Aspen but perhaps he got his tail under it.