this isnt technically an injury, but its the worst pain ive ever experienced so here goes.
A few years ago (6 ish) i got a verrucae ( a kind of foot wart infection thing) and it refused to go away.
The gel from the pharmacist was useless so i went to a pro, a chiropodist or something.
So i get there and lie down on the chair, she pulls a razer on my foot and physically cuts off the dead skin. This just tickled a bit so i thought no big deal, until i felt something warm running down my foot, i looked and saw my foot had a river of blood coming from the verrucae. And then she kept digging, into new skin, which hurt like a *****, for about half an hour. Now if this isnt bad enough, well it got much worse.
She got two tubs of crystals, looked a bit like salt. she put a bit of each directly into the cut in the new skin. It was acid. Fucking acid. still dont get how it was crystallized but whatever. didnt sleep that night, i can tell you that.
In fact the worst pain from the whole experience is that i went 21 times, once per week, and when i refused to go the verrucae disappeared within the week.