ぼくは知らないし、気にもしない。の英語

I don't know, nor do I care.

I don't know and don't want to know.

I don't know and I don't want to know.

To put it succinctly, I don't know, and I don't want to know.

I don't know that.

I know nothing.

I don't know anything.

Everyone knows I wouldn’t do that.

Although it seems like I know about that I don't know anything.

I don't really know either.

I am not concerned about that.

Don't ask me, I really have no clue.

I know nothing to the contrary.

I didn't know that.

I have no idea of the matter―not the faintest idea of the matter―not the slightest knowledge of the matter.

As for me,

For my part,

Myself,

I don't care.

That just doesn't make sense to me.

I admit to being careless.

I admit that I was careless.

That is not my idea of him.

I don't know a lot about that.

I don't know either of them.

I wouldn't be able to answer something like that.

I'll probably pretend not to know about it.

I don't quite know how it happened.

I haven't got the slightest [faintest] idea about it.

I must see for myself―see with my own eyes―convince myself by personal inspection.