People tell me you start with ice to slow blood flow which slows the swelling (swelling is due to all the dead cell membranes clogging the capillaries, which then kills more cells which clog more capillaries, which is why it continues to swell for a while.) Hitting ti with ice for 12 hours after can ease that a lot. The start with heat which helps break down the dead cells membranes and stimulates blood flow to move all the dead junk out of there and brings in repair materials.

Or ... as I often do ... just leave it be and show off your bad-ass bruise.