The Cat

I was out on a hike tonight and picked up a little snake. Sort of looks like a midland brown snake according to a species guide online but I may be wrong. Anyway, a little boy who was holding it dropped it in the grass and it burrowed. The boy started to pull it out, not gently, and yanked it from the grass. I took it back and noticed it had these bumps around its tail, but they would fix themselves after a few moments. Is this natural or is it injured? Would it have been from the boy's roughness with it?