Sounds like she is developing an abscess in one of the milk ducts--probably due to a blockage like Elaine suggested. If it is going to abscess the warm compresses will "bring it to a head"--it will rupture and drain very nasty pus--I have had this--very gross. Or your vet may need to lance it and drain it. You need to keep pups off that nipple--but you should hand express it your self with each feed so it does not get engorged. You can tape a very large bandaid over it to keep pups off. If it should abscess and rupture and drain you need to clean it several times a day keeping the hole open so it can continue to drain and heal from the inside out. If it closes off it will continue to fill with pus. The bitch also needs to be placed on antibiotics like amp or amox or possibly cephalexin keeping in mind that the abx will pass into the milk so must be safe for pups.

Miriam Olesen
http://www.omegabulldogs.shutterfly.com/

You might try some warm (not hot) compresses to the breast for several minutes and then trying to gently express the nipple, and I'd keep the pups off that nipple in case there is some mastitis. Perhaps others have additional suggestions.

I took Boston to the Vet this morning, he lanced the lump and a ton of fluid came out. He also opened up the hole and told me to drain it twice a day. Now he said not to let the pups use it anymore, but its still filling with milk. I try to get as much out as I can but it seems to always be full. What if one of the pups gets to it, when I'm not looking, will it be very serious?

Thanks for all your help,

Jeremy

ps--It was Boston's 4th Birthday Today, which I don't think she enjoyed one bit!