my ews certificate is issued by naib tehsildar..as there is only naib tehsildar where i am living..is it valid in documents verification

Tajinder,

You've attained an EWS certificate provided by a governing authority of tehsildar office. In your place of residence there's only a naib tehsildar and the officer knowing of all his responsibilities, approved your application for EWS certificate. So, there must not be any such concerns. The EWS certificate that you've attained is the proof from the the highest authority in your tehsildar that provides you this reservation.

So, don't worry and go with it. If there's some serious doubts in your mind, for more clarification you can contact the main tehsildar regarding this.

Hope this helps!