ABSCESS.

An abscess is a collection of pus circumscribed in a sac enclosed within the tissue of the body.
CAUSES:
Abscesses that can be seen or felt under the skin are caused in many cases by fighting with another dog. A tooth penetrates the skin causing damage to the underlying tissue. Bacteria are deposited in the tissue at the time of penetration. Foreign bodies such as a splinter of wood or grass seed or another common cause 0f abscesses in dogs. Sometimes dogs develop internal abscesses on the liver, lungs, and elsewhere, following a generalised bacterial infection.
Next time I will talk about signs of abscess in your dog. Cheers.