Nation state does not mean the same things as state or country.
States that are mostly nation states: Japan, Korea, Mongolia, Thailand, Portugal, China, Morocco, Romania, Timor-Leste.
States that are mostly not nation states: Australia, United States, Singapore, Germany, South Africa, Russia, Brazil, Mexico, New Zealand, Canada, the UK, actually most of them really.
Nations without states: Kurds, Inuits, Uyghur, Zulus, Catalans.
A state is more like a 'nation state' inasmuch as most or nearly all of its population comes from a single ethnic, religious, linguistic or cultural group, and perceives itself as culturally united.
In the modern world this is pretty uncommon as so many countries grew their boundaries to absorb a range of different groups in large numbers, or have since enjoyed significant levels of immigration.
Now you need never look silly by accidentally using 'nation state' as a synonym for state. It's not my place to say whether I'm a hero, I leave that for others to judge.