if it's deep it might be an idea to get yourself to a&e.
If not, well, keep it clean, maybe put something over it etc, sure you know the drill (if not, I can try to explain/direct you in the right general direction)
Sorry to make it even gloomier, but I'm not good either. I just cut myself, for the first time.
Don't want to lecture you or anything (but here goes anyway), but cutting yourself is a very very bad idea. Once you've started it can be hard to stop. Plus you can end up with a ton of scars. Try and find something more positive to do when you feel bad (think you said something about writing poetry).