its called a hygroma and its pretty common....change the dogs bedding. give it something soft to lay on shavings or such. its mostly cosmetic and i recommend not draining.... any time you do you risk introducing infection.... but im not a vet.
WOW...you said something smart with out the A$$ on the end
I learned something. Injecting DMSO works great
cut the bottle with a lil water first to activate the heat reacton!