Please go to your doctor and show it to them! Because if it does turn out to be cancerous, it needs treating as soon as possible as it can spread into the lymphatic system and further up to the lungs and other places. I'm writing this from bed at home having had a testicle removed today myself as it is strongly thought to be cancerous. It can be embarrassing of course for some people to have to drop their trousers in front of medical professionals. But I can assure you that they will make you feel entirely comfortable and reassured as soon as you arrive and start getting checked over. If you need to ask any questions etc or need any advice from my own experience I'd be only too happy to help. But first of all, get an emergency doctors' appointment and if that proves unattainable get yourself to the local hospital and chuck yourself in A&E as you will definitely be seen that day. It's a big step to take I know, but if the thing spreads into the lungs, for instance, it gets a lot worse. If it is testicular cancer, it has about the same survival rate as the common cold if caught early enough!!! As for telling your parents, get the tests done first and don't let the pressure of telling them stop you from getting tested. You can tell your parents afterwards when you know more yourself. Testicular cancer is a very rare form so your odds are pretty good from the outset anyway and it may pass without the need to tell your parents anything. I myself didn't tell my parents until the day before I had a major test done (when cancer was highly suspected already). In my case it was not through embarrassment (as my family are a medical bunch anyway) that I didn't tell them, more to stop them worrying needlessly. I wouldn't normally advocate keeping silent about such things for long of course, but if it lessens the pressure on you, so you can get checked first then do as you feel you need to. I hope it's not the worst case scenario (which in itself, believe me, isn't all that bad) but please get checked as soon as you can (today/tomorrow). Good luck
This may be a little late as I wrote the comment before I'd signed up or noticed the date but I'll post it anyway just in case: