As you have noticed swelling of the left eye after getting injured in a boxing match. The condition you are having is black eyes or ecchymosis
if the eyeylids and it is because of collection of blood in the layers of the eyelids.
You cannot put a incision on the eyelids to remove the blood from eyelidsin this condition.
The treatment advised is cold
compress by placing ice packs over the closed eye lids to hasten the absorption of blood and analgesic
drugs to decrease the pain.
You need to undergo eye examination by a ophthalmologist to rule out any associated injuries of the eye as the ecchymosis of eye lids by itself is self limiting and will subside over 4-6 weeks even without treatment.