1.
( especially BrE ) used to tell sb not to worry or be upset :
Have you broken it? Never mind, we can buy another one.
2.
used to suggest that sth is not important :
This isn't where I intended to take you—but never mind, it's just as good.
3.
used to emphasize that what is true about the first thing you have said is even more true about the second
SYN let alone :
I never thought she'd win once, never mind twice!