Hi ,
Is the ulcer recurring at the same spot ?
If yes,then IMHO in the pic it looks more like an injury to the inner surface of cheek.
The injury can occur due to 2 reasons -
1- biting cheek while chewing , 2- sharp edge of the tooth rubbing against the cheek.
in such a case Becosules will be less useful.
Next Steps
Meanwhile visit a Dentist to check for any sharp edges of the adjoining teeth.U might want to apply a gel (prescribed by a dentist) on the ulcer to relieve pain and help healing of the ulcer.