But never mind that; it doesn't matter.

可别介; 有关系。

Never mind the tortuous explanation; tell me in plain English, are you coming or not?

别拐弯抹角地解释了, 直率地告诉我, 你来不来?

Never mind the interruption; proceed with your story.

不要理睬别人的插话, 继续讲你的故事。

Never mind the washing-up—we haven’t got time.

别管盘子的事情了，我们时间不够了。

Never mind the exact technical specification; just give us a free translation of what the machine can do.

别在要有精确的技术说明, 只要把那机器的功用给我们译可以了。

Never mind the expense!

不用担心费用！