I can't make much out. I'm guessing that you are referring to the area with the dark discoloration.
How long has it been there?
How fast did it grow?
What are his housing conditions?
Is it irritated and sensitive?
Can you get better pictures? (none of us are vets but clear pictures could solve it right away)
I know money is tight with everyone (especially with winter setting in) but sometimes its best to run to a vet early to save yourself a really big problem down the road. Let us know...