Thank you for your reply.
The most likely cause of your symptoms (development of this tender knot) is a blocked Salivary Gland.
There are 3 sets of salivary glands...the largest one is right in front of the ear (called parotid gland), the 2 smaller ones, called 'sublingual glands' and 'submandibular glands', lie deep in the floor of the mouth. All of the glands produce saliva.
It is most likely that the gland that got blocked is the one called "submandibular gland". It is located on the outer side underneath the tongue. The most common cause of gland blockage is formation of a tiny stone. Stone blocks the outlet of saliva causing the gland to swell up and get inflamed (and sometimes infected).
There is no danger in this condition other then discomfort, however, the stone does need to be removed to alleviate symptoms.
I would suggest that you make an appointment to see your dentist. A dentist would be the best specialist to have your symptoms looked at and treated.
I hope you find this information helpful. If you need any clarification or have any additional questions, please let me know and I will be glad to assist you further.
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