Greetings!
Usually this problem occurs when there is an abscess (collection of pus) under the tooth,this usually occurs when there is a cavity present on the tooth,
Sometimes loose and unhealthy gums can also lead to entry of bacteria.
Rest can be judged by clinic examination.
Next Steps
You need to go to a 3-5 course of antibiotics ,
Avoid chewing from that side,
Ice pack application-5-10 min patting every 1-2 hours,6-7 times a day.
An extraction is usually done in this case.
But a root canal can be done if dental and periodontal condition allows.
Health Tips
Don’t apply anything hot and avoid eating too hot as it can flare up the swelling.