What can you do if a tattoo hurts and has pus coming out of it?

Sue!

I partially agree with the above stated answer...if the fault is that of the shop, and not your poor aftercare regiment. In the instance of what you are describing, you may have received a staph infection from the tattoo, for which the blame could easily be yours as well as the artist's. In any event, consult a dermatologist, get on some antibiotics, and notify the shop that you got this done at that this is happening and go from there. In the event that you got this done in someones house with improperly sterilized, or just outright dirty gear, then still consult a dermatologist and get on antibiotics...but the next time that you are going to go that route, look at the scarred hideousness on your skin and think next time.