What to do if i have red gums under just one tooth?

See your dentist: May be inflammation of the tissue due to a piece of food getting stuck beneath the gum margin, could be a problem with that particular tooth (deep decay) resulting in a root abscess. It is best to see your dentist to determine the exact cause and to determine a treatment plan.

See your dentist: The diagnosis will require a clinical examination and X-rays. This could be as benign as a gingival irritation or even as a complex access from an infection that could be either tooth related or gum related. Many ethiologies could cause this and the treatment will depend on that cause. Please see your dentist as these things don't get better by themselves.

See your dentist: Gum disease can affect a single tooth or several teeth and if left untreated, may lead to infection and tooth loss. See your dentist for evaluation, x-rays and treatment.