We have had a number of cats coming in recently with nasty infections from cat scratches and bites. Several of the injuries had occurred a week before, and the owners thought that once the wounds closed over they were healed. However, that is never the case. Without treatment the infection then grows in the tissue and causes an abscess and damage to the underlying  tissue. Treatment usually includes antibiotics. The secret here is to get your cat checked out and antibiotics started immediately, that way you reduce the need for anaesthetic and surgery. Cats that get into fights are more at risk from contracting viral diseases such as Feline Infectious Viraemia FIV which causes other health risks.