thanks for your question, the features what you are giving suggests you have pulpitis in lower tooth that causes pain while eating sweet or hot or cold food.. this needs to be diagnosed by taking radiographs....and you might also have myofacial pain syndrome secondary to disc disorder of the jaw joint...you can take piroxicam tablet 2omg twice daily on first day and once daily for next 4 days an long with a muscle relaxant... avoid eating hard things, dont open your mouth too wide, take soft diet for 15 days..consult a dentist for needful... i hope my answer will help you...you can also give hot foamentation(dip towel in warm water and sqeeze it and place it over the affected area)..