Visit dentist, he will take x-ray for you to confirm the problem.

As your age is 21 years and you say there is no decay or cavity, then it could be your third molar or last molar which is erupting.. this tooth erupts after the age of 19, but a proper diagnosis is necessary... Visit a nearby dentist

Treatment depends on proper diagnosis.

There might be tooth decay which won't be visible to you. You need to visit a dentist for that. When you eat, food might get stuck in the decayed part and cause you pain. For pain take Tab. Ketorol DT (6) 2 tabs at once. Mix in 1 cup of water and consume it. Take whenever you have pain.

There could be a cavity. Until you visit a dentist take a painkiller like combiflam sos. Medicine will give only temporary relief.

Hello. Whenever there is pain while chewing its an indication that the infection is present at the very base of the tooth. Most of the time these infections start as small cavities and when ignored over time lead to such infections. Sometimes the cavities may start between two teeth and therefore may not be visible while you look at yourself in the mirror. You need to go to your dentist and get this checked out. Most probably you need to get an RCT but with out an Xray I cannot be 100% certain. You can take basic pain medication till the time you visit the dentist, but taking medication is only to delay the treatment and not to treat your present problem.

A picture of affected area will help For now Take tab diclomol SOS followed by antibiotics that can be only given once the diagnosis is clear For detail treatment plan and medications kindly contact me on personal chat box Thank you

It must be upper tooth or any of the last tooth ...that's y you are not able to see any infected area . This type of pain is often diagnosed by dentist only .