It is best to figure out what it is before treating with medicine. If it is an abscess, lancing it and squeezing out the pus, then giving a broad spectrum antibiotic would be best. Most good antibiotics come from vets. If it is canker which is a protozoan, a drug like metronidazole, fishzole, or General Cure from Petsmart would treat that.yes i could be pus, but i feel bad for her ,and i dont know what to give her to cure