没事儿 (méishìr) It doesn’t Matter /Nothing
The character “没 (méi)” means not or be without; “事 (shì)” means matter
and “儿 (ér)” here is a suffix.
Example:
A: Bùhǎoyìsi, wǒ bùxiǎoxīn bǎ nǐ de bǐ nònghuài le.
不好意思，我不小心把你的笔弄坏了。
I’ m sorry; I broke your pen by mistake.
B: Méishìr.
没事儿。
It doesn’t matter.