There is a carious tooth might goes infected deep so there is swelling n pus ,so tooth become little tender n occluded from socket so there is difficulty while closing your mouth n chewing.
Next Steps
visit a dentist get iopa xrays done doc will disoclude the teeth 1st n do the needful painless procedure which is best for you as off taking care of your physical n medical condition.
Health Tips
avoid chewing on that side n don't do warm saline gargle