気にしないよ。
I don't care a pin.
I don't mind that.
Who would care?
もう気にしてないよ。
気にするなよ。
I'm not the least bit worried about it.
I'm not the least bit worried.
I don't care [mind] a chip.
I don't mind that.
もう気にしない。
I don't care anymore.
Never mind about that.