Look man, you have to go to a doctor.
I have large hydroceles around both of my testicles and am getting surgery on Friday. I had to get an ultrasound, urine sample, and after that went to see a urologist.
Apparently mine have no known cause, I don't have any virus or anything, they're just there.
If you're worried about people looking at your balls, think of me, my left testicle is as long as my hand span. (Well it's not actually, but it appears to be that big).
The ultrasound really wasn't as weird as I thought it would be, and I didn't even have to expose myself to my doctor. (Only the urologist.)
So really, I'm extremely glad I went to see the doctor, even though mine are not harmless (just fucking awkward), I would be thirty times more worried if they were hard lumps. If they are hard lumps that means you have tumours (hard lumps in the testicles, there are no nodes down there to swell [only in the inner side of the pelvis]), cancerous or otherwise you MUST get them looked at.
And really, your father is really stupid. If you've got cancer, cost shouldn't be an issue, and he's a selfish twat.