Good question. It actually depends on all kindsa different things. We'll try and give you some basic tips:
- Ask if your friend is cutting to kill himself. If so, you might have an emergency on your hands.
- Ask your friend if he's going to be okay for the night. That way, when you get off the computer later, you'll sleep better (as long as he said he could be okay.)
- If your friend says he's NOT going to be okay, ask him to call for help.
- If you know this person's real name, phone number, and/or address, you can always send the police to do a welfare check if you're worried about your friend's safety.
- If your friend says he's cutting without intending to kill himself, tell him there's help out there for that. Ask him to get help.
- If he refuses to get help, don't let him bog you down with depressing stories about his self-injury. Keep insisting that he needs to get help.
- Refer him here: http://www.selfinjury.com/. Lots of info on self-injury that can help.
Basically, when you have limited info on someone, there's only so much you can do. Remember that this person's safety isn't your responsibility, so you don't have to come up with a cure for him. You can support him by telling him he should try to stop and get some help. Otherwise, it's up to him to make the right decision. :( It's annoying, but it's the way it is.
We hope this helped a bit. Take care of yourself.