Cavity just started on left upper tooth.

Some people naturally have more sensitive teeth than others due to thinner enamel. In many cases, the tooth’s enamel can be worn down from brushing your teeth too hard, using a hard toothbrush, grinding teeth at night, eating or drinking acidic foods and beverages etc. Tooth decay, broken teeth, chipped teeth can leave the dentin of the tooth exposed, causing sensitivity. You can ask to your dentist about prescription toothpaste and mouthwash. They may also apply fluoride gel or desensitizing agents. However, If you have persistent and severe sensitivity, an x-ray should be taken to determine the cause. For wisdom tooth pain, clinical and radiographic examination is necessary to determine the cause of pain and course of treatment.

Visit the dentist for definite clinical evaluation and treatment.

Use softer toothbrush and brush more gently. Limit acidic foods from your diet.