Well, first, if this is the first time in many years you have been riding, it's probably some sort of physical thing from the bike. You also may want to ask the LBS to check the fit and setup of your bike. And check your cycling pants. Loose ones can allow things to get twisted up.

That said, this also could be the biking activity drawing attention to something else. If your testicles are important to you, see a doctor. Else, take the advice of others here who have
1) likely no medical degree
2) have not done a physical exam and have no test results
3) may be prejudiced by there own experience, which may have completely different causes that your issue

Seriously. Steve Jobs trolled the internet for new-age miracle cures for a cancer that was eminently treatable, with a high likelihood of success, using conventional therapies. This delayed him getting the standard treatment, and this delay killed him. See a doc!