that happened to me a few times. i woke up thinking i'd gone sleepwalking and slaughtered myself in the process or something. the best was having someone over and them waking up and screaming.
I was drunk once and cut my arm on a broken window pane. I fell into bed and into the arms of hops-infused morpheus - when I awoke, there were streaks of rust-colored dried blood all over my bedsheets, pillowcase, at first I was like, WTG!?1?! and then I remembered.