There is absolutely nothing wrong with adding an occasional ultrasound to your surveillance routine. Some guys here get one annually, or so, on their surviving testicle. I got one at the one year mark.
That being said, it is rather funny how everything acts up and feels sore just before an oncologist visit. I never hesitate to bring up all the stuff, but most of it goes away upon an "All Clear". There is also the possibility that you are checking it often? That could cause soreness.
All to say that it could be a good many things prior to another presentation in the other testicle. Bring it up to the doc but don't worry too much and don't be scared to push for the ultrasound.
Friendship is born at that moment when one person says to another; "What! You too? I thought I was the only one." - C.S Lewis
“Experience: that most brutal of teachers. But you learn, my God do you learn.” - C.S. Lewis
Mass found 11/20/08
Left I/O 11/25/08
Pathology: Seminoma, Stage 1
Surveillance: All Clear since