it is/was nothing idiom informal
别担心；没什么要紧的
used to tell someone not to worry about, or place special value on, what you are doing or have done
"You seem very upset." "No, no, it's nothing - I'm OK." “你看上去很不安。”“不，不，没什么，我很好。”
"It was so nice of you to look after the baby all day." "Oh, it was nothing, I enjoyed it." “谢谢你一整天照顾宝宝。”“哦，没什么，愿意效劳。”