Possible. Also possible it's his testes, or a BM. Or a cyst, or a few other things.
Good call on the Dr. :) If you get very worried, remember...the nurse advice line at your local hosp is "open" 24/7.
They can also tell u if it's something to treat at home, wait for an appointment, or run to the ER. My son actually presented the classic symptoms for a twisted testicle, which we found out 8pm friday of a 3 day weekend. The nurse advice line sent us to the ER...and BOY I have never never been seen faster. "Stat! A baby boy with something wrong to his balls!" Talk about USHERED through the male staffed ER. <laughing> Turned out to be a highly virulent infection, NOT a twisted testicle. It theoretically COULD have waited 3 days. But apparently while day one was numb, after that it would have been screaming pain. So we got the piece of mind, and my son got out of the pain. Whew!Close one!