Depends, sometimes they heal sometimes not. When they don't you need them removed. If it's the first time he's had one, I would go to the vet. My dog had them his whole life, some got to be the size of tennis balls, but didn't burst for years.
Found similar thing on Princess Buttercup last night. I expressed most of the gunk & cleaned with Hibiclens. It's much improved this morning but headed to the vet to see it antibiotics might be in order. On a funny side note, I just told her "don't scratch your sore ear baby!" She gave me the dirtiest look known to man & I'm fairly certain she even rolled her eyes at me as she went back to scratching her good ear.My first Basset Chloe has a serbacious cyst, one day I thought I had a tick as I found a patch that looked like coffe grounds, I remember taking her to the vet, vet rubbing her finger over it knocking the top off then a huge amount of what was like cottage cheese comming out. Freaked me out! She had surgery on hers eventually!