Hi.. Thanks for the query.. As per your complain red, painful bumps in various parts of mouth can be due to causes like Apthous Stomaitis, Bullous Pemphegoid or Viral infection causing cold sores or fever blisters.. It can be caused due to a number of reasons like Stress, Nutritional Deficiency [Iron, Vitamin B12 and Folic acid] , hormonal changes, acid reflux, tongue trauma due to some sharp teeth or tongue biting habit, excessive intake of sour and citrus foods, uncontrolled diabetes and other immunocompromised conditions etc.. You need to consult an Oral Physician or a general dentist in this regard to get evaluated and treated.. For apthous ulcer you can do warm saline gargles Gargles with 1:1 solution of benadryl and milk of magnesia can help.. Apply numbing gel over the sore for relief from pain especially during eating.. Take a multivitamin tablet for a period of 15 days.. Avoid spicy, sour and acidic foods.. In case if still the condition does not subside the physician can prescribe you to take a Steroid course as it it the ultimate treatment in case if nothing else works.. Hope this helps.. Regards..