For black eye, you need to see your doctor when you are having a hard time seeing any doctor. Seek treatment if your vision is impaired, you have pain in your eye, you are light sensitive, double or blurred vision.
Otherwise the following is how to block a black eye.
Pack it in ice
Cold works in two ways; helps keeping the swelling down and by constricting the blood vessels, helps decrease the internal bleeding which causes the black and blue colour. Apply an ice pack for the first 24 to 48 hours. If your eyes is swollen shut, use it for 10 minutes every 2 hours the first day. To prepare the ice pack, just crushed ice in a plastic bag and tape it to the forehead to prevent putting pressure on the eye.
Hold a cold soda can against the eye intermittently (5 to 10 minutes every 15 minutes) until you can get some ice on it. Nevertheless make sure the can is clean and then hold it lightly against your cheek, not your eye. Do not put any pressure on you eyeball.
Take acetaminophen if you need a pain reliever. Aspirin will make you ending up with a bigger bruises as it is an anticoagulant, which means the blood will not clot as well.
Do not blow your nose
Blowing your nose could cause your face to blow up like a balloon. The injury may fracture the bone of the eye socket. Blowing your nose can force air out of your sinus adjacent to the socket. The air gets injected under your skin and makes the eyelids swell even more and increase the chance of infection.
Most black eyes will last about a week and nothing can be done to disguise it totally. Thus you have to live with it. When it starts to heal, it will turn green, then yellow and finally it just disappears.