Blue balls is real and can be uncomfortable. It's not just something sex pests made up to coerce people. And it almost always goes away within an hour. I think it's something about semen getting loaded in to the vas deferens and the vas deferens not being set up to handle being full for prolonged periods, something like that. Apparently the going theory is that it's caused by blood flowing in to the testicles and penis during arousal, but then the body not sending the signal to stop or reverse or whatever that process that usually occurs with orgasm or ejaculation. The whole system is reasonably robust though so it eventually sorts itself out.

Apparently it's hardly ever studied, probably because it almost always resolves on it's own within an hour. I'm not even sure it can be consistently induced, It's been pretty random for me.

I think it's important to know that it's real, both because people need to be able to read the feedback they're getting from their reproductive system, and because if someone tries to pressure you with it you can tell them to walk it off or go sit on some frozen peas because it'll sort itself out before too long.

That said, sudden unexpected pain in the testicles should always be taken seriously as it may be a symptom of testicular torsion. If it's severe or persists for more than an hour or two you should go to the ER to get checked out.