YOU SAID:

Realized I held the blade inside my back

INTO JAPANESE

背中に刃を入れていたことに気づいた

BACK INTO ENGLISH

I realized I had a blade in my back

INTO JAPANESE

背中に刃物があることに気づいた

BACK INTO ENGLISH

I noticed a knife on my back

INTO JAPANESE

背中にナイフがあるのに気づいた

BACK INTO ENGLISH

I noticed a knife on my back