Hi, pain in decayed tooth is suggestive of pulpits. As the tooth cavity grows deeper over time it reaches nerve of the tooth causing pain. We need oral check-up & x-ray to confirm that then we can decide upon treatment. RCT is the treatment of choice in such cases, if delayed further might need extraction of tooth. Better to visit some endodontist and get it treated as soon as possible. For temporary relief you can take analgesics.

Depending on the extent of the decay, a filling or RCT will be done to save the tooth or else it would be extracted if decay is too much. Sooner you get it treated the better are the chances of retaining the natural tooth.

Do visit a dentist nearby , then treatment ll vary according to the tooth condition whether u need root canal treatment or extraction followed by replacement ... Don neglect the problem , tooth decay ll not get reduced until it is treated...