Oh mannnnn.
You, I, the UK Government, Penn & Teller, Roger Federer.... we can all call Scotland whatever we want in the vernacular. Roger Federer can call it "The tartan-y fiefdom of Scotland" if he wants to. I can call it "The super-state republic of Scotland" if I want to. The UK government can call it "The nation of Scotland" if it wants to.
But in reality, under the accepted international definition of the term, Scotland is not a nation. Nor a country.
As I said, many people within and outside Germany still refer to "the Kingdom of Bavaria". Do you think this must be taken in its proper, internationally-accepted meaning: that Bavaria is ruled by a King/Queen - and thus, since a King/Queen is a head of state, Bavaria must be a nation state in its own right? Or can you see the difference between a vernacular colloquial usage of these sorts of terms (nation, country, Kingdom, etc) on the one hand, and the formal internationally-agreed definition of these sorts of terms on the other hand? And that under the proper definition of terms, Bavaria is no more or less than a federal region of Germany?
By all means, feel free to keep calling Scotland a nation or a country if you like. It isn't in fact either, but there's no harm in using those terms in a colloquial manner (unless and until you need to come face to face with international law.....).