Small gel-like circular substance/object attached to my leg

I am 16M, about 5'10 and 135 pounds. I was changing socks when I noticed this weird circular thing attached to my right leg. It's not exactly clear, more white than anything. It's about the same size as the tip of my pinky finger. I had to essentially peel (for lack of better terms) it off of my leg, and it hurt, enough to make me wince a little. There's no mark or blood or anything on my leg from where it was, and it's the only one I've found on my body. I need help identifying what it could possibly be and what steps I could take to avoid it happening again, thank you