black dots on penis?

i 18m tried a new … “activity” today. it resulted in a lot of blood, more than normal, inside my penis (so the skin was very red; no external blood) every time i did it and after a few times some red dots showed up on the head. i quit because i was worried.

i’ve had light bruises before and so i didn’t worry about it. but now, only a couple hours later, the dots are black. i know bruises can turn black but isn’t that after healing for a bit? or is this not a bruise and something more serious? could’ve i have damaged something?