Hello there...I can understand your concern. If a little gel is swallowed, it wont cause amy harm. Mouth ulcers can occur due to a number of reasons like
vitamin deficiency, herpes simplex infection, pemphigus, candidiasis. It is important to determine the cause. Also if the lesions are small and few, they usually spontaneously heal on their own. If it's not healing, then consult a dermatologist for further evaluation.