"Nothing particular" versus "Nothing in particular"

What is the difference between "Nothing particular" and "Nothing in particular"?

I have been told that "Nothing particular" is grammatically incorrect and that "Nothing in particular" should be used instead.

What exactly is the difference between these two statements and is "Nothing particular" actually grammatically incorrect?

Are there any scenarios where one would be preferable over the other?

"Nothing particular" is a perfectly well-formed NP, parallel to "nothing unusual". It just happens not to be a familiar expression, and its meaning is derivable from its components.

"Nothing in particular" is an idiom, whose meaning is not readily derivable from "particular" (though it is from that of "in particular").