Aphthous ulcers are ulcers that form on the mucous membranes. They are also called aphthae, aphthosis, aphthous stomatitis and canker sores.
Aphthous ulcers are typically recurrent round or oval sores or ulcers inside the mouth on areas where the skin is not tightly bound to the underlying bone, such as on the inside of the lips and cheeks or underneath the tongue. They can also affect the genitalia in males and females.
Recurrent aphthous ulcers are mostly a minor nuisance, but they are associated with significant health problems in some people.
BORAX 30- Painful whitish blisters in the mouth which bleed easily. Fungus like growth in the mouth
MURIATIC ACID 30- Foul smell in the mouth with soreness of the teeth and gums
HYDRASTIS CAN 30- Apthae and ulceration of the membranes of mouth. Tongue is yellowish in color and there is constipation
MERURIUS SOL 30- Painful blisters with foul smell from the mouth. Increased saliva
NITRIC ACID- 30-Painful blisters with offensive and acrid saliva
LACHESIS 30- Severe form of apthae. Swollen dums with burning. Gums spongy and bleed easily
SULPHURIC ACID 30- Gums bleed easily. Pyorrhoea. Tongue swollen. Excessive salivation
ARSENICUM ALB 30-  Burning blisters. Sips water frequently
THUJA OCC 1M- White blisters on the sides close to root of the tongue. Painful  and sore . This remedy  has  aspecific antibacterial action and destroys the fungus growth

EXTERNAL – Use Borax or Hydrastis glycerole