hello kumar shanu
you have not mentioned your age and duration of swelling
The area you are telling doesnt have much structures ...1st ---you feel it when you apply pressure so that can be lymph
node or the muscle inside which is attached to the jaw bone you are pressing so you feel pressure and pain everywhere and there may also be carious tooth inside your mouth or an unerupted tooth
which is making the muscle irritated and tender.
Secondly just ruling out a lymph node if its not sore to touch is not correct.
it can be enlarged salivary gland
see ent specialist
that will help.....it not possible then do regular mouthwash,and stop self examining