Hi, im 15 and have a similiar thing. Im a one sport athlete, soccer. I havent messed around with any girls but my current girlfriend and me are getting closer. I masterbate 0-2 times a day... I havent told anyone yet, dont have the courage to tell my dad.
I have the same problem, but on the right side. I've looked up many different things and it could be sperm cells inside of the Vas Deferens(seeing how you used to masturbate and mess around with girls), this could be because of a small cut or slit on the inside of the tube, your body doesn't recognize this so it sends white blood cells to take care of it. The white blood cells cause the Vas Deferen to puff out. It is most likely not cancer, since I haven't read up on any type of cancer for the Vas Deferens, but I would recomend seeing your doctor just to verify. Also, it could just be an infection and cleared up in a few days with anti-biotics. Or it could just be a capalary, which is mistaken for lumps and bumps inside of the scrotum.
Good luck.
(P.S. I'm not a doctor, I'm just a 15 year-old kid, so if any of this is wrong I do apologize but my diagnosis can be wrong. So do not blame me for anything that might go wrong. Even though nothing probably will.)
not in but right next too sorry