The swelling in last tooth region is due to eruption of last tooth i.e wisdom tooth..get an x- ray done to see the condition of tooth and gums around that region..If the problem is due to last tooth only, extraction may have to be done but after getting the x ray done as tooth can be saved too by root canal treatment if infection is there..Treatment will depend once you visit the dentist..
Next Steps
visit the dentist and get x ray done
Health Tips
Warm saline gargles twice a day