How do you bruise yourself?

Well since bruises take longer to appear- up to a whole day- they may not give you the release that cutting provides. While I do not condone self harming, I know that you will do it whether I tell you to or not, and since bruises leave no scar and may save you from embarrassment or future pain from all the memories a scar leaves, I will suggest some type of suction applied hard and for a long while, like a minute or two. That will give an instant bruise- just like a hickey works, by breaking open all the little capillaries. Bruising is easier to achieve by blunt force in boney areas or areas of increased bloodflow- think back of the hand or inside of the arm.

Why do you need to cut yourself at all? It makes it worse

Don't do it.