Nation-State is synonymous with sovereignty. This is so when we realize the fact that sovereignty is the absolute power of the state to exercise supreme legal authority over its own affairs within its territory without any form of external control.
A state has a definite geographical territory in which it is situated and has boundaries. It is sovereign, independent and a republic. It has also a human population who inhabit the given area.
On the other hand, a nation, like a state is a collection of people who live in a definite geographical area and has a sovereign government.