NBA great Paul Pierce found himself in the hospital on Friday ... after suffering an incredibly gnarly finger injury that resulted in a ton of blood and a few broken bones.

The Boston Celtics legend alerted his fans of his current medical status just minutes ago ... showing him decked out in a gown while in a hospital bed.

The posts that followed were so bad, we wish he hadn't shared them at all. But he did ... so here we are reporting on it.

Pierce snapped nasty shots of the injury ... with (what appears to be) his right ring fingertip pointed away from his thumb. Another pic is zoomed in on the other side of his phalange, which was busted right open.

Despite how cringeworthy it looked, the Hall of Famer insisted he's doing just fine.

"I'm good by the way just broke a couple fingers gonna have surgery on one," The Truth said on Instagram.