Don't let it bother you; put it out of your mind.
I don't want to continue with this conversation (usually used in frustration or anger).
It doesn't matter.
A conventional reply to an expression of gratitude.
Absolutely not; I forbid it or it is impossible.
It does not bother me; I am not concerned.
It was no problem; not at all; you're welcome.
Do not worry, I will do it.