What causes rid of a blood blister on hand?

Keep it covered: This is usually caused by a sever pinch to the skin that breaks a small blood vessel under the skin, but does not cut the top layer of skin. A small amount of blood then accumulates under the skin. It will go away with time. You can apply ice to help with any swelling. Keep it covered with a bandaide. Resist the temptation to puncture it with a needle. This could cause an infection.