Jonah 3:11 sez:
And God saw their works, that they turned from their evil way; and God repented of the evil, that he had said that he would do unto them; and he did it not.
God is allowed to change his mind (via "regret") when He's demonstrating His Amazing Grace and Infinite Mercy.
However, He's also immutable, which means He cannot change His mind, per 1 Samuel 15:29:
"And also the Glory of Israel will not lie or change His mind; for He is not a man that He should change His mind."
Ehhh, just don't think about it: it'll make your life MUCH easier as a JW.
PS regret is a 'surprise' emotion, hence inconsistent for an omniscient being who knows future events (I like to say that someone cannot sneak up on God and go, "BOO!!" to elicit a startle response from Him, since God already knows you're coming).
Like I say, don't think about that one, either.... Get behind me, Logic! (eh, I mean Satan!)