Dear Practo user, it seems that your tooth (molar) has some long standing infection and needs to be treated. Once a capped tooth is swollen and tender, there has to be an insidious cause of your pain. An X ray would be helpful to know the cause of pain in the tooth and determine the treatment.
Next Steps
Kindly visit your dentist at your earliest and let him/her examine the problem region. Clinical examination with the aid of an X ray will be helpful in diagnosing and treating your condition.