“没什么大不了”的英文翻译，要地道的俚语式的。

no big deal(not important, no problem, not a serious matter)
没什么大不了
It's no big deal.
这没什么大不了的。
losing his job was no light matter.
丢了他的工作没什么大不了的。
I don’t think her mistake amounts to much.
我认为她的错误没什么大不了的。
It doesn't weigh much with me whether you go or not.
你去不去对我来说没什么大不了。
It do not weigh much with me whether you go or not.
你去不去对我来说没什么大不了。
It does not weigh much with me whether you go or not.
你去不去对我来说没什么大不了。
It's no big deal! I can find another job anytime.
没什么大不了的！我随时都可以找到另一份工作。

it's not a big deal
老友记里经常出现的,最地道的俚语

It's nothing at all.
it's not a big deal~

It's no big deal.

it's noting seirous