Honestly saying such kind of questions in fact 90% of questions are very difficult for a doctor to answer without clinical examination.  The answers we provide can not pin point the cause without clinical examination and lab investigations

Treatment depends on size n frequency of the ulcers..go n visit dentist asap

Hello sir....       Blisters occurs due to many cause        ** Ulcer(apthous stomatitis)        ** Mucocele (due to cheek biting,lip biting,traumatic injury to salivary gland)        **viral infection(herpangina,herpes simplex....   blisters are of two types    1.blood filled     2.Fluid filled ** Blood filled  blisters are due to tarumatic injury,herpes infection, low platelet count,allergic reaction to citrus foods... ** Fluid filled blisters are  mucocele due to lip biting,cheek biting which cause traumatic injury to salivary gland.... Usually small blister which is temporary and painless do not need much attention IF the blister is recurrent and large, you need medical attention immediately.. HOME REMEDIES for small fluid filled blisters: Breaking up the habit of lip biting,cheek biting, stress,anxious...      

Consult a dentist or a doctor when the blisters appear. Clinical examination required for diagnosis