Hi.. Can understand your concern.. As per your query the swelling in the salivary gland under the tongue may be due to swelling of either submandibular or sublingual salivary gland.. The swollen salivary glands may be due to a number of reasons . Most common for under the tongue salivary gland swelling is a blocked salivary gland duct.. When the duct is blocked the saliva which has to reach the mouth goes back to the gland due to blockage in the duct.. Other reason can be infection (bacterial or viral) causing swelling of gland as well as foul smell in mouth.. Other reasons are cysts , tumours and some autoimmune conditions. Treatment depends on the exact cause and that can be diagnosed by clinical evaluation and laboratory investigations ( if required) I would suggest you to see a doctor soon and get evaluated so that treatment can be planned accordingly.. But I would suggest you not to delay the treatment to prevent future complications.. Thanks and regards..