What next? According to livestrong: "Lack of certain B vitamins can precipitate mouth sores or cause skin irritation in and around the mouth. Mouth sores have many causes, but taking certain B vitamins can prevent or alleviate some types."
What next? I have no idea how it actually works, when my wife gave up smoking she had mouth ulcers you would only wish on sex offenders, we looked into it and many people who give up smoking suffered the same problem, the advice from across the internet was vitamin B, it worked. A guess at vitamin B to counter ulcers from creatine would be my first approach, both items cost peanuts and it seems pretty logical.