Hello, I suspect that the most likely cause is trauma. This can include hard foods, exposure to hot temperatures, or habits. I suggest that you monitor the area. Rinse with warm salt water, avoid irritants, avoid acidic and spicy foods, and stick to a soft diet to assist healing. If your tissue is dehydrated or you have any respiratory or sinus complication, this could be a contributing factor. If you have repeat episodes and can not associate the occurance with a trigger, schedule a visit with your dentist for a clinical evaluation. Systemic factors may need evaluation with blood tests. Your medical and dental history will need to be reviewed as well. Thank you for your inquiry. I hope the area will continue to heal on its own.