Hi sir....   Your history seems you have salivary stone (sialolith) that which is medically called as Sialolithiosis    Sialolithiosis__Formation of salivary gland stone usually within salivary gland duct... As you have swelling in the floor of mouth , the gland probably involved is SUBMANDIBUAR SALIVARY GLAND. SIGNS AND SYMPTOMS: ** Intermittent pain  usually before mealtime and subsides afterwards **Intermittent swelling usually before meal time and subsides afterwards **Tenderness of involved salivary gland ** PALPABLE HARD  LUMP  if the stone is located near end of the duct, IF THE STONE IS NEAR THE SUBMANDIBULAR DUCT,YOU CAN FEEL THE LUMP IN THE FLOOR OF THE MOUTH(UNDER THE TONGUE) **Lack of saliva(Total obstruction) **Erythema(Redness) of floor of the mouth ** Pus discharge **Bad breathe ** Cervical lymph node enlargement CAUSES OF SIALADENITIS: **Abnormal calcium metabolism ** Dehydration ** oropharyngeal infection ** Reduced salivary flow rate **Acidic Ph of saliva DIAGNOSIS.. Mostly by **physical examination and history **X_ray of salivary gland( sialogram) **Ultrasound

Your symptoms suggest that you may have a sialolith or a salivary stone. Please visit an Oral Medicine specialist or an Oral Surgeon. They might ask for specific x-rays or a scan to determine the exact location of the stone. Depending on the same, the stone can be removed.

You have to consult a dentist. From your question the exact location of the lump is not clear. If it is related to the RCT tooth it indicates reinfection. An X-ray is required. If it is in the floor of the mouth and not the gum, it could be a mucocele or salivary gland cyst. Clinical examination required for proper diagnosis