Hi.. It could be because of tooth decay or worn out enamel called cervical abrasion. It can be solved by doing composite fillings or by root canal as needed. Regards

Hello, If you think there is decay in the tooth it is best to go to the dentist because it will only continue to get worse. If it is from clenching take some advil to alleviate the soreness. If the pain is from gums u have to clean your teeth very smoothly and avoid contact with gum because the cleaning with contact of gum may be lead to some recision of gum that which cause a pain and uncomfortably so that avoid that and if you have very sensitive teeth to hot and cold use Sensodine tooth past.