sensitivity could be due to many a reasons like tooth erosion, tooth abrasion,micro leakage in the filling ,tooth decay, exposed root surface.after checkup with dentist if you any of these conditions then filling or root canal treatment will be suggested.The depth of problem can be accesed by taking an x ray.
Next Steps
Try to use Desensitizing tooth paste for temporary relif
Health Tips
if sentivity is sever avoid hot, cold and citrus types of food until you are treated