Thanks for your query.
After reading your symptoms, I am quite certain that you have a blockage either in your salivary gland
itself or the salivary gland duct as the swelling occurs after eating food. There is no correlation with the lymph
I would suggest you to get a contrast CT along with a sialogram
of salivary gland of sub mandibular / submental region. Treatment plan will depend on your diagnostic findings. If the blockage is in duct then it can be removed intra orally under local anesthesia
I would recommend that you visit your doctor and get the test done at the earliest in order to avoid infection.
Hope this answers your query. If you have any more queries, do let me know.