What is wrong with my royal python!??

[Kingcobra070]

This is hard to explain so i will do my best...My royal python shed about a week ago and i noticed that he had substrate stuck to his back after his shed, i didnt think anything of it because i thought his skin may have still been sticky after shed, and since havnt had a chance to take a decent look until today (3 days after his shed) when i realised that the substrate was still stuck to his back. So i put him into the bath for a short while and then lifted him out to have a closer look. This is when i stupidly thought that it was just some left shed and decided to gently pull up a small piece above an unusual circle of yellow and noticed that it was bloody underneath and the yellow isnt usually there anyway. if anyone knows what this could be, im thinking a fungal infection at the moment, please, please let me know...i plan to take him to the person i bought him from as he is very clued up on reptiles and will probably know what it is...but i am very desperate to know...thanks!