Well, I beleive the best thing you could do is get an appointment with your family doctor as soon as possibe to make sure. It's always better safe than sorry. Testicular cancer is nothing to play around with and earlier diagnosing is the best way for a quicker cure if it is something.
Don't be embarassed. I had a sonogram done of my testicles last month just to make sure. I've allready been diagnosed with Hodgkins Lymphoma, and I will not take anything lightly again.
Good luck, and more than likely it will be a normal growth.