A black eye is just a bruise
in the tissue around and under they eye. This means, unfortunately, that it heals just like any bruise - it requires time and patients, usually days to weeks, to clear up. There is very little that you can do to make the bruise go away more quickly.
If there is significant swelling around the eye, what you can do is use warm compresses to improve circulation and help decrease the swelling more quickly. Similarly, taking an over the counter anti inflammatory medication like ibuprofen or naproxen may help to reduce the puffiness more rapidly.
Unfortunately, these approaches will do nothing to help the color of the bruise, which will just have to go away on its own. Some people feel that they can make the bruising go away more quickly if they elevate their heads while they sleep, but there is no evidence that this actually works. In short, what most people do is to resort to covering up the bruising with makeup and just waiting for it to heal up on its own.
For more information about this issue, please ask your primary care doctor
! Good luck!