The word Scotch has several meanings, but it should never be used as an adjective to refer to a person or object from Scotland. The only exception is that the word is acceptable as part of certain compound names, such as Scotch whisky, Scotch mist or Scotch broth.
Words such as Scotchman or Scotchwoman are obsolete and frowned upon by people from Scotland. The correct words to use are Scottish or Scots. It would be wrong, for example, to say “The Scotch weather is frequently atrocious” but it would be quite correct to say “The Scottish weather is frequently atrocious”. Similarly, the Scottish newspaper is The Scotsman, not The “Scotchman”.
The word Scotch on its own is (as well as being a registered trade name) often used as a shortened form of “Scotch whisky”. Therefore, it is just about permissible to say “Scotch man”, as in “I’m a Scotch man, myself”, but that would mean someone who enjoys or prefers to drink Scotch whisky rather than someone from Scotland.
Footnote : “Whisky” and “whiskey” are often used interchangeably, but the two spellings identify the origin of the spirit. In the UK, “whisky” means the drink from Scotland, whereas “whiskey” is used when the source is Ireland. More widely, “whisky” is also used when referring to the Canadian and Japanese drinks and “whiskey” is generally used to refer to the drink when it is from the USA.