HELLO SIR.... Sensitivity in teeth is due to many cause,..... **dental caries **cervical abrasion **occlusal erosion ** Gum recession which expose root surface ** Root caries Though you dont have any visible cariesYOU NEED TO VIST DENTIST to check for any proximal caries ( between the teeth) both clinically and radiologically....

Visit a dentist to get the area examined clinically as well as with x ray for proper diagnosis..It is not essential that the cavity in teeth will be visible from above as a deep cavity may be present proximally( in between two teeth) which might be creating pain as well as sensitivity in particular region..Attrition or abrasion i.e chipping of enamel of tooth might have created facets leading to sensitivity..So visit a dentist asap

Get an x-ray done, because sometimes the cavity develops in between the two teeth that may not be visible. Or sometimes the sensitivity could be because of enamel chipping due to heavy brushing. So it's better to show to a dentist and get an x-ray done for a better diagnosis.