Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concern... As per your complain blood blisters on gums occurs commonly due to viral infection [herpes], other causes can be bacterial infection in gums causing gingival abscess, allergic reactions to medications or foods,herpengina etc.. As other ulcers have resolved and one is persistent you need to get evaluated by a dentist that whether it is a dental abscess caused by a deeply infected and decayed tooth leading to pus formation below the root tips or is a gingival or periodontal ulcer or is due to any infection like herpes. Treatment can be decided depending upon the cause.. In case of infected tooth root canal treatment or extraction followed by antibiotics is the treatment.. For gum infection scaling followed by antibiotics oral and topical will relieve.. In case of other infections like Herpes or any other infection treatment of the same will relieve.. But until you get a proper evaluation and necessary investigations done and get a confirmatory diagnosis done proper treatment cannot be advised.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora.