Okay, i'm am starting to get a little worried now. I am 16 years old and I have this small piece of skin that overlaps the hole on my penis. It basically looks like the inside of the hole is swelling a bit. I'm verry worried its cancerous or something. I am masterbating alot, could that be it? Just swelling from that? I can urinate fine though.
It could be the result of a meatal ulcer (meatal stenosis) a common complication from circumcision. Or it may just be a slight abnormality or even something to do with the frenulum. From your description the first is my best guess. You could search for images of that condition but only a doctor can tell you for sure.
It's definitely nothing to do with masturbation or everyone would have one.