It doesn't cause any pain, and can be moved a bit, and it's appearance leads me to think it's a pimple or cyst deep in the foreskin
A couple days after it appeared my real problem
started. I noticed that the foreskin had swollen slightly over the top side of the glans shortly after I masturbated. It didn't cause any pain, and felt like a buildup of fluid, so I assumed I went too rough on the poor guy and it was swelling due to irritation.