Sensitivity could be due to loss of enamel layer or a deep cavity that seems to b small superficially. Get it check by a professional ASAP.
Next Steps
Visit your nearest dentist. If you are in hyderabad you may visit our clinic The Dental Room for help.
Health Tips
In case of cervical abrasions, kindly stop brushing vigourously which might accelarate enamel wear over a time period.