<s>[INST] I have a puss filled bump in my mouth...the lower part between the connection of your tongue underneath and your lower teeth.  Its probably 1/2 inch below the gum line.  It keeps coming back after it pops, its been going on for about week and half or so. [/INST] Hi. Welcome to Chat Doctor. I read your query. The pus on the lingual side of lower teeth can be due to tooth or gum infection. Check if there is any cavity in corresponding teeth. Or if you had any trauma to lower teeth, any toothbrush injury or calculus. I suggest you to visit a dentist and get an x-ray done. If it is due to periapical infection, you may need RCT of affected tooth. In case of gum infection, you may need curettage and scaling of that portion of gums. Both are minor procedures, usually done under local anesthesia. Do warm saline rinses. This will help in Chat Doctor.  Your dentist will prescribe you antibiotics and painkillers. Brush twice daily. Take healthy diet, vitamins, minerals. Hope the answer helps you. Thank you! </s>