'know', 'no', or 'right'?

That depends upon what you mean to say. Number 2 is incorrect, in any context. Numbers 1 and 3 contradict one another, although each stands as an acceptable sentence on its own merit.

And both 1 and 3 would probably be more correct with commas:

"I already told you, no."

"I already told you, right?"

OK ThanQ