Your problem and age is mostly suggestive of a third molar erruption.
However many other reasons like trauma, deep cavity, pockets etc could be the cause for this.
A clinical checkup is recommended
Based on the diagnosis treatment will be decided
Next Steps
visit a nearby dentist asap
donot delay the treatment
Health Tips
don't self medicate yourself
for temporary pain relief use cold compression and do Luke warm salt water gaurgle 3-5 times a day.
In case of severe unbearable pain- take a dolo650 tablet after food.