hey, I’m 17 years old, I think I may have the same problem as a couple of you guys, I went and saw the doctor after noticing what felt like a lump and swelling in my right testical and he sent me to the urologist, he explained that when I lift heavy weights with a full bladder, sometimes urine can be released from the bladder under pressure (such as lifting or removing a tier) and travel down the sperm tubes and irritate my testical, only on the right also.

He told me that it was symptomatic meaning it will come and go, it doesn’t really bother me unless it becomes painful, then after that it’s usually just rest.
I highly recommend seeing a doctor, hey iv had to see him 4 times now on 4 different occasions for this same problem, and it’s really not as bad as you think.
Note: I found that if I masturbated whilst my testical was enlarged, it didn’t help my cause just made things worse and more painful after ejaculation.