for inflamation:
when it aches put an ice pack on it,
3 min on then 3 min off

for pain:
take Advil or Tylenol (use as recomended on the bottle)

Just remember that Advil is an anti-inflammatory and Tylenol is only an analgesic. If you've got a friend who is a doctor ask them about using Advil differently when you're healing from a recent injury. Usually involves doubling the dose for two weeks and taking it every 4 hours you're awake. But watch out for stomach issues and if you have a history of liver issues it is not a good idea at all.

The reason to wait for the swelling to go all the way back down is that if you don't then you body will make scar tissue in your knuckle to protect it if you start training on it again while it is swollen. Scar tissue is made of shorter fibers than regular connective tissue so it reduces blood flow and increases your chances of arthritis later on in life.

So try not to hit anything with that knuckle until it returns to normal if you'd like to have regular hands the rest of your life.

Disclaimer: I am not a doctor nor do I play on on TV (IANADNDIPOOTV)
happy training, Dana