A tooth abscess is a bacterial infection starting at the root of the tooth and often affects the gums. These sores can develop because a tooth abscess often begins with tooth decay or a cavity that expands and fills the entire pulp chamber. As with any other infection, pus develops as white blood cells fight the microbes.
This pus swells up under the skin, and in this case, the gum, and develops into a sore. You may see white or pink pimple-like sores develop on the gum above the tooth in the form of an abscess. There may or may not be a pain when this sore is touched. If the sore pops, it could leak unpleasant tasting and smelling discharge throughout the mouth. It is important to pay attention to these sores before they pop and take steps to avoid a rupture.