A black eye is a relatively common result of injury
to the face or the head, caused when blood and other fluids collect in the space around the eye; swelling and dark discoloration result-hence, the name "black eye."
Most black eyes are relatively minor injuries and heal of their own.
Despite the name, "black eye," the eye itself is not usually injured.
The skin around the eye is very loose, with mostly fat underneath. This makes it an ideal site for fluid to accumulate. The effects of gravity also help to swell this part of the face.
Apply ice locally
Take anti inflammatories like ibuprofen
400 mg three times a day for 3 to 5 days.
It shall take 2 to 3 weeks to go completely.