I had a wart frozen off. It formed a boil full of puss, not blood. You're supposed to lance it with a sterilized needle when it puffs up to drain the fluid. Poke a hole in either end and allow the goop inside to drain out. You may need to push on it some. It'll fill up again and you'll need to lance it again.

And by sterilized needle I mean wiped in rubbing alcohol and then held up to a flame.