Can it be a callus?

Hi, I noticed a small bump on my lower back, exaclty on the top of my butt cheek. It s as big as a normal coin and seems to be reddish in the middle and dark clored skin o the outer part. I think it may be a callus as it feels like a cushion in the inner core, and eventhough it might seem strnage for aplace of a callus there, in my case I think it could be as I tend to slouch a lot while sitting applying alot of friction and pressure on my tail bone. In fact it use to hurt me a lot when I spent alot of time sitting this way. This bump does hurt a bit when I squash it, but not when I press it, and it feels less sensitive than the skin around it. Should I be concerned, or just start sitting properly and soak hot water for it to reduce? THANKS A LOT