Hard Ball Found on Chest (Please help!)

I’m 23, male, 5 foot 8, 170 pounds, on accutane. I found this hard ball on the side of my pec. It’s moveable, very slightly sensitive, and somewhat close to my armpit. Not detectable by sight, only by feel. Skin looks normal. I believe it’s tissue bound, doesn’t feel attached to bone at all. My main concern is I only felt this after extreme sleep deprivation. I stayed up for ~35hours straight hiking an extremely tall mountain. I was carrying a backpack the whole time which was stressing my back and traps out. Once I finally got sleep, I woke up and felt the ball. I’m very conscious of my health so I would’ve felt this earlier if it was there. I even recall feeling my chest about a week ago and I didn’t detect it. Does anyone know what this might be? If it doesn’t shrink quickly I’m going to get it checked out.