I Have Had This Happen Before Only On The Left

I have had this happen before only on the left side of my neck right below the mandible. Usually I am eating and all the sudden I get this sort of sour feeling and then all the sudden the gland will puff up. It is tender to the touch. Any thing I should worry about? Is this some kind of salivary rock irritating the gland. Generally it goes back down in a day. Suggestions? It helps a little if I massage it, but not sure what to do. I'm a pretty tough ole gal, but this is annoying and starting to concern me. This time the left side is doing it.
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