ive told this one before.. a friend of mine was fucking his wife, he was all into it from behind saying he was in "pornstar mode." needless to say he missed the re-entry and slammed right into her pelvic bone or something. he said his dick swelled up and turned black as night. i believe he heard a snap or something.
he went to the doctors and they told him they would make an incision around the head of the penis and roll the skin down and drain the ***** out of it and sew it back up. he left as soon as the doctor left the room. he said it healed itself. i wouldnt want to risk it myself, but apparenntly it worked out for him.
myself, the most injuries ive sustained from fucking are zipper scratches. big time. my girl was on top of me and took my dick out of my pants via zipper and we still had out clothes on. i didnt feel it till i came but omfg. it hurt like a ****** fucker, it was all tore up, scratched and even a little *****. it happened a couple of times and the next couple of days after that, it burned when i put it in her so sex kinda hurt. but we still did it.
other than that happening, the most ive got has bruising and pain between my dick and my belly from her pelvic bone. she was pretty thin, 5'10'' 105 pounds. she was a grinder too. i was always bruised there. fishing on a boat and leaning on the rail was ****** everytime, but well worth it.