Swelling and pain in the flesh behind a large tooth may be due to pericoronitis, gingivitis or apiculitis. Pericoronitis is a condition in which the gums are red, swollen and bleeding due to the accumulation of food debris and bacterial growth around the crown of the tooth, especially when wisdom teeth are not erupted enough to induce pericoronitis of the wisdom teeth. You can use mouthwash to rinse your mouth and rinse around the gums to relieve the symptoms. Gingivitis is caused by tartar or soft tartar stimulation leading to bleeding from brushing or eating, sometimes with obvious pain, and requires scaling and medication to improve. Periapical periodontitis is a sign of inflammation of the nerve of the tooth, pus in the gums, pain when eating, and a feeling of tooth elongation, requiring root canal treatment. Pericoronitis, gingivitis, and periapical inflammation can all lead to swollen and painful gums, and the exact cause needs to be examined by a dentist to confirm the diagnosis.