I had him at the vet lastnight,he said if it is blood filled it should go down in time an if he lanced it he could bleed to death,but if it is puss it will get bigger and start to make a head and he will lance it then,but he says he will be ok
It's a hymertoma(sp) basically a blood blister, Easy to sort at home with a decent sized syringe needle, pop it in and gently squeeze around the lump and the blood will drain out, they sometimes refill.
Can't believe the vet didn't atleast try to drain it as above, very strange
I was tempted to try and drain it my self ,but my vet is an real old t