Hi.. Can understand your concern.. As per your complain a painful swollen gland under the tongue can be due to a few causes which affect the sub-mandibular salivary gland which is one of the major salivary gland like: It can be due to infection in the salivary gland leading to formation of pus which causes swelling and pain.. There can be obstruction in the salivary gland duct due to formation of crystalline stones from minerals present in saliva . It leads to back flow of saliva into the gland leading to formation of painful swelling and the pain can increase during eating.. Other causes of swelling in salivary gland can be formation of cysts , tumours both cancerous and non cancerous, Autoimmune disease like Sjogren s syndrome. I would suggest you to consult a dentist and get evaluated for the exact cause of the swelling and treatment can be planned accordingly.. For infections antibiotic treatment can be healing.. For blockage of ducts exploration of the location of stones and removal by either pushing the stones towards the ducts and removing them,while large stones can be removed surgically... Tumors, cysts can be removed surgically.. For Sjogrens syndrome stimulation of saliva flow by using Pilocarpine medicine and sour candies and sugarfree chewing gums can help.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora..