Testicular Agony - Men's health issue not a play issue

It's possible you could have ruptured an epidydimus or vas, or have intense swelling and pressure to the point where it is close to rupture. I have had a vasectomy, so these are issues I deal with periodically, but it is possible to have them even if you are intact. Especially if there was something physically blocking or restricting your urethra (you didn't mention that, but just saying).

As the pain reduces, maybe you can pinpoint more precisely where the pain was coming from. That could help identify the problem.

It could also just be a super intense case of good old fashioned blue balls. The vascular congestion created by prolonged teasing and abstinence causes discomfort like being kicked in the balls, with pain radiating from the testicle up into the abdomin (the blood vessels follow that path). With mild blue balls, this pain fades relatively quickly in the hours that follow ejaculation. But if it was particularly nasty, it could still be painful the next day after ejaculation.

Testicular torsion is an extremely serious emergency. It is normally excruciatingly painful and would normally leave no question of it being an emergency. It can threaten fetility permanently, as well as testicular health in general (untreated can require the removal of an affected testicle). If you were able to stand and function at all, it probably wasn't this. But pay attention for numbness or lingering intense shocks of pain.. if it happens, treat it as an emergency and seek medical assistance immediately.