1
general::
1. Don't worry about something, don't trouble yourself, it doesn't matter. For example, Never mind what I said, it wasn't important, or Never mind, you can always take the driver's test again. This expression employs mind in the sense of "care about something," a usage dating from the late 1700s. 2. Also, never you mind. Don't concern yourself with that, it's none of your business, as in Never you mind where I plan to buy the new TV. [Early 1800s]
American Heritage Idioms
2
general::
Phrase(s): Never mind!
Forget it!; It’s not important! • Sally: What did you say? Jane: Never mind! It wasn’t important. • John: I tried to get the book you wanted, but they didn’t have it. Shall I try another store? Mary: No, never mind.
McGrawhill's American Idioms And Phrasal Verbs