You can apply some numbing gels such as mucopain etc . If the pain from the ulcer is too bad currently we use laser procedure to accelerate the Healing process and can reduce pain also . Regarding stomach ache consult a physician as digestive conditions can reflect in ones mouth . So rather than treating mouth ulcer, diagnosing the underlying cause for the ulcer is the correct way to go about . For example Even a constipation, upper respiratory infection, gastric reflux etc all can cause pain in the tongue and mouth ulcers . If your general health is taken care of mouth ulcers will vanish and not recur .