What Causes Black Circular Spots On Buttock?

My husband has two black circular spots on his buttock that were not previously there, and they are the diameter of a cigarette. He has a history of sadism & masochism and previously has displayed what looked like whip marks or light bruising from paddles. He thinks he is hiding this behavior, but occasionally I see things that suggest that he is engaging in this risky behavior. He is 68 and has parkinsonism with Lewy Bodies, reducing his appreciation of the risks involved. Is there any benign reason for the sudden appearance of such spots? His fetish has been spanking in the past, but I am concerned that he may have been burned by a cigarette. The rest of the buttock looked somewhat lumpy rather than smooth, so I am suspecting padding then burns. He will deny everything if I confront him directly. We will be seeing a counselor, so right now, I want to know if he is at immediate risk if it is burned tissue.