Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain and explanation of symptoms it seems you had a deeply decayed tooth that involved the nerves and the inflammation of the nerves has led to severe pain.As there way no treatment done slowly the nerves and blood vessels got necrosed making the tooth non-vital[dead] so the pain stopped. But now there is formation of DENTAL ABSCESS as when the infection proceeded below the root tips of the tooth there is pus formation and at times the pus and infection perforates the bone and the pus gets accumulated in the soft tissues and in your case it is appearing as a painful blister over the gums.. You need not to worry and just consult a Dentist and get evaluated clinically as well as get an X ray done and if the condition of the tooth is considerable to be saved get a ROOT CANAL TREATMENT done followed by capping of tooth.. In case it cannot be saved it should be extracted.. As of now you can take Augmentin 625mg three times a day, Ibuprofen 400mg three times a day and Pantoprazole 40 mg once in the morning empty stomach, all these has to be taken for 5 days and within this consult a dentist.. Avoid chewing from the affected side and avoid extremely hot and cold foods and liquids.. Hope this information helps.. If you find the answer helpful please give me a Five Star Review and click on found the answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora..