my rat had an abses under her arm about 1 month or two ago and she popped hers too. we took her to the vet and they gave her some antibiotics and told us to leave it to rest and see what happens. they also told us to give her some live yogurt because the bacteria in it helps their immune system and helps them fight the infection. get her too your vet as soon as possible. im sure your ratty will recover and return to full health like mine has done good luck keep me updated
good luck keep me updated 