A swelling, inthe size of a grape, at left part of my lower jaw, only at the time of eating and it is visible for 3 or 5minits,no pain,no other proble?

Salivary gland: This sounds like sialoadenitis which may be due to a sialoith. Those are fancy words for a inflammation of the salivary gland possibly due to a stone. There are other causes which should be fully evaluated by an ear nose and throat physician. This may require a sialogram or other imaging procedure but a physical exam and history is required first.

Not sure of questio: What is the question. You should see your primary physician to look at it. Questions would include duration, associated symptoms -- eg sore throat, ear ache, etc. A physical exam and history are the start...

Swelling in jaw: This sounds like you have a blocked salivary duct. See an oral surgeon for treatment.