The true meaning of 'ethnicity' is pretty synonymous with 'culture'. A people is not only culture and ethnicity but also genetic heritage, including race. 'Pakistanis' are no nation but Muhammadist members of the Indian nation, the Indian people. An important distiction in all this, is the one between nationality and Citizenship.
The State is not a nation but a consituted legal person. The State is a signed paper document that is, in a legal sense, literally a person. That person is the owner of the land, which is to say the true monarch is a legal person, a signed paper document. Now, the organization The State has members. These members are called 'Citizens'. Being a member of a formal organization, is different from being a member of a nation. The State lies when it calls itself 'nation'.