Jesse's pigs
Adult Guinea Pig
Looks like a spot of fungal to me. Difficult to judge the body part from the picture!
No I can see why you thought it was on his testicles lol I do apologise getting the pics of his ear clear enough for you to see the spot and nose were tricky- I swear he knows! XLooks like a spot of fungal to me. Difficult to judge the body part from the picture!