Does anybody know why clenching/kegel while the penis is erected is painful?

So you can have an erection with no pain, then you clench strong and an instant pain appears.

I try to never clench, but sometimes is impossible, I mean it's like involuntary action, for example while ejaculating or maybe if you have a nte and touch the clothes.

So what's going on inside the penis that makes that pain to appear so instantaneously? You pass from no pain to a instant/short pain.
What's the mechanics in the clenching? Does Clenching introduces more blood and penis gets a bit bigger so that stretch the plaque?

I'd like to understand.

I would suspect it's nerve pain.  No basis for that other than most of my flaccid pain seems to move around, which I think indicates nerve involvement.

nemo

It could possibly be nerve pain or from the little extra blood that is forced into the penis making it slightly larger and stretching things a bit. Sometimes when I clench my pc muscle I can physically see my glans get larger.