Dear practo user It seems cheek bite due to molar teeth. Need oral cleaning treatment. Wait and watch  else do mild teeth grinding through dentist.

Welcome To Practo , This is your Dentist - As per the image attached , Sir you need a Scaling as there would be inflammed gums from the plaque and tartar deposition. Let me know if any history of smoking and whether the cheek feels leathery. If not Scaling will help. But due to corona outbreak you wont be having this procedure done. So need to wait. Till then -: - Tab Metrogyl ER 1 Tab bd x 5 days - Keterol Dt Sos - Rexidine M Forte Gel (gum massage) - Betadine mouthwash ,gargle in lukewarm water 2-3 times a day. -Use a soft bristle tooth brush and brush gently in vertical motion from gums to teeth's edge. I hope it helped. You will be fine nothing to worry about . Have a Good day Thank's Alot.

Locate the region in pic. Warm salt water gargle. Dologel CT, 5 times/day, In clean mouth use finger/fresh ear bud for applying the gel, keep applied on gum area for 3 mins, meanwhile not to swallow the saliva, rinse mouth thoroughly after 3 minutes. Not to eat anything for next 20 minutes.

It might be because of traumatic cheek bite or third molar or wisdom tooth problem. As your clinical picture is not that much sufficient to tell you the diagnosis. As you are saying, pus is there then it might be wisdom tooth improper position so you need to do warm water along with salt mixed gargles 4 to 5 times in a day, it will relieve your problem. Consume vit b supplements or tablets two times in a day for 7 days and in picture ..it is seen that there is traumatic cheek bite in the region of third molar or wisdom tooth. Apply Rexidine m forte gel there, for 3 to 4 times in a day. And if you are saying pus is there, Take a antibiotic course.

No need of anything just east some good fruits and healthy diets