なんのきなしに
unintentionally; inadvertently; calmly; casually
Also written 何の気無しに、なんの気なしに
Expression, Adverb
なんの気きなしに言いっただけで、別べつに悪気わるぎがあってのことではありません。
I just said so without thinking much about it. I didn't mean anything serious.