Try holding onto a bunch of icecubes really tight, it will hurt but not harmful.
Twanging elastic bands on your wrists.
Drawing your pain on your body with felt tip pens.
Have a list of at least ten things you will commit to do before you do it, that may help calm you down, like taking a bath, reading a book, listening to music, include in that list ringing a friend or relative. Hopefully when you get to the end of that list the urge will have past. It invariably does, self harm is often an impulsive action.
If it does not help you keep committing not to do it for the next ten minutes, when you get to the end of that ten minutes commit to the next ten minutes. In the meantime try make sure you are around someone else and if you can't take yourself to a&e or to the doctors and explain how you feel.
I used to self harm but keeping to the above principals helped me to stop and i haven't done it for ten years even though sporadically i still do get urges. The moment of relief is not worth the lifetime of scars.
I hope that helps
