Numbness/discomfort in left side of groin.
Just after I got into bed earlier tonight, I noticed that my left testicle, and a little area above and to the left (sort of where the leg meets the groin, could just be deeper in the scrotum) feels numb and uncomfortable. It's not expliticitly painful or sore. (There was a very slight sting at some points, depending on what position I was lying in--on my right side in particular--and an occasional sting here or there randomly.) My left testicle seemed to shrink, and then swell up a little, then return to normal size. It seemed to be hanging lower than it should have compared to my right one (taking into account the fact that testicles tend to hang unevenly anyway) for a bit, as well.
I don't feel any lumps, so I don't think it's cancer, and since there's no pain I don't think it's testicular torsion. I'm not sure what else it could be. . .I read something about people getting vericose veins in the scrotum, but I don't really know what I'm supposed to be feeling for, and there doesn't seem to be much of a difference between right & left sides (but again, I don't know what I'm supposed to be looking for). I'm 21 (i.e. past puberty/growing pains), and there's no chance of this being an STD.
Any clues as to what this might be? I assume that a trip to the doctor would be in order if this persists, but if it goes away soon, should I still get a checkup just to be sure it's not a sign of something serious?