Hello,
This condition is known as Pericoronitis, your wisdom tooth is erupting in the wrong direction, known as bucally placed ( towards the cheek), you need to get an XRay done & get it extracted.
Next Steps
Get an XRay done (OPG)
Health Tips
Rinse with lukewarm water with a pinch of salt (2-3 times/day)
Rinse with betadiene gargle twice a day for 5 days.
Maintain hygiene & avoid eating from this side.