I have a swollen frenulum under my tongue. what could be the cause of this. i had an xray and there was no stone.what else could cause this?

Frenulum: It can be swollen from a viral infection like a canker sore. You could have torn it partially, or you could have trauma from food or hot drinks.

Injury suspected: Perhaps an injury from very hot food or beverage or too much suction while kissing causing injury.

Depends: A clogged salivary gland due to a NON stone could be possible. Food irritation, local trauma, a hot drink burn could cause swelling. Please get rechecked by your doctor as history and exam are going to be very key to a diagnosis.