What does this japanese character mean?
 

hi please help me! i know i'm an idiot. i was drunken and made this tattoo. i made it abroad. now i don't know what it means. can someone help me?

ps: i even don't know wether the tattoo is chinese or japanese

Probably it's the kanji for "shimesu" (示す) that means to show, to point out. It also can be "shimeshi" (示し) which would mean discipline.

Please someone correct me if I'm wrong.

It was originally a Chinese character, and Remy is right, 示 means to show or reveal. Guess you got lucky, you could have ended up with a lot worse.