Do not… please do not self harm! It will hurt and it will always hurt. I've been self harming for about a year now. I'm currently over 1 month clean. It is not a road you want to go down. You will feel pain. You cannot escape pain when you cut. This is the whole point of cutting.

Alternatives -
Say "I'll self harm in 15 minutes if I still want to" and keep going for periods of 15 minutes till the urge fades.
Complete something you've been putting off.
Search ridiculous things on the internet.
Watch YouTube.
Or TV/movie.
Go to the plark, play on the swings.
Carry safe rather than sharp things.
Cook.
Play a sport.
Doodle on sheets of paper.
Play a computer game or painting programs such as photoshop.
Learn to swear in another language
Hunt for things on Ebay or Amazon.
Have a nice long chat with someone.
Be kind to somebody.
Have a warm lush bubble bath!
etc...
The limit is your imagination!