I suspect my gelding is a cryptorchid. His testosterone just came back at 115 ng/dL. In 2020, his test was 11 ng/dL.  We will be doing the hCG next to confirm but there isn't much out there regarding if this can be painful.  If he requires surgery, I will, of course do it.  His behaviors are more childlike than studley. He rides with no issues but gets feisty when you approach his junk.  I have succeed ready to go if we rule out man problems and he just has hind gut issues.  Anyone have experience with pain? Surgery? Similar behaviors? Thanks!

I suspected a gelding that was sent to me was a cryp. It was

comfirmed hy the HCG test. Owner didn't want to do surgery.

 I would test your gelding but it really doesn't sound like it's likely.  Especially this time of year, even legit geldings can act studdy when they're around mares. 
Sensitive in the flank area is usually a  stifle or digestiion