Below a lower left molar (that does have a cavity) there is some gum swelling. it feels soft and squishy. no pain whatsoever. comes and goes... ?

Abscess: You have an abscess. It may be from a non vital too th nerve or a periodontal pocket. Please see a dentist to have it evaluated and treated. Failure to do so may result in the loss of the tooth.

Probably infection: Abscess. Will not go away by itself . Pills can't fix it. Can only spread and damage bone, gums, other organ systems. See a Dentist ASAP.

Chronic Infection: The gum swelling that you describe is most likely chronic dental infection originating from a decayed lower left molar. See a dentist for examination, x-ray and treatment options.

Needs immediate care: You need to see your dentist immediately. You have an abscess and it's only a matter of time before it becomes extremely painful and more virulent. Hopefully the tooth can still be saved. Call your dentist immediately!