poke yourself in the eye, its fun.
but seriously, your question is very vauge, so i will just say if you or someone you know is cutting or smashing their head into the wall, its time to see a counselor. if youre doing it to hurt or punish yourself, its a suicidal gesture that should be taken seriously.
I think that if someone was doing it for attention, they would put it on display and show a lot of people, going, oooh, look, i carved a frowny face in my forearm.
If someone is hiding this, then it definatley warrents attention. Show them love and try to get them help.