I'm not going to immediately tell my boss about my promotion.
Why won't you tell him?
I'm so sick of my boss, he's so stupid and ridiculously annoying.
You should not hide that promotion from him. He has the right to know. You shouldn't make him look bad for it.
I don't care what you say I'm not going to tell him and thats that!
Your boss is going to eventually find out. It's good to be professional towards your (soon to be former) boss when you're leaving them. You never know if you'll work under them again.