I had a black eye for lease three weeks what should i do?

Prolonged: A black eye from trauma to the eye area is due to bleeding that occured and leaked under the skin to be low the eye. In time the color goes from black and blue to yellowish as the blood slowly breaks down. However the discoloration may take up to two weeks to fade. In your case it's taking longer but should fade completely soon unless there was more bleeding. See your MD if you're still concerned.