Hi welcome to Health care magic forum. Dont worry about the gland, it would have formed long back due to infection of the teeth mouth or hea.
said that your mouth is fine means that is it. you have no caries or ulcers in the mouth.
Head louse may cause a gland some times. i advise you to consult a physician and say though it is harm less i want to quit it. He will give medicines
along with vitamin C
for desolving the gland. If it is there also it wont harm you.
If it becomes hard grows in a short period you should sea a doctor. Thanks for calling.