mayalso be a burn--- hot drink or food.we call them pizza burns. warm salt water rinses for a week. if it gets worse, or you get a fever, see a dentist sooner
It sounds like the gum tissue behind your upper front teeth was traumatized some how.Sometimes this occurs because of your bite. I would suggest that you rinse with warm salt water as much as you can,give it about a week and if it doesn't get better see your dentist.