Hi, I have gone through your question carefully and understood your concerns. The mouth ulcer you got in your mouth seems to be due to viral infection, especially, if you have had flu like symptoms at that time. If the ulcer will appear again, I d advise to consult with your family doctor and to run following diagnostic tests: - complete blood count to exclude anemia - culture of mouth swab to exclude fungal infection For the moment, I advise to keep a good oral hygiene and avoid having too hot drinks or foods. All the best!