Good day Dr. I have a 22days old baby boy with a pink spot at the back of his head neck, so I would like to know what must I do to remove it,?

Nothing. Without seeing the spot in person it's difficult to provide a certain diagnosis. Many babies are born with "stork bites" -red/salmon colored areas - on the back of their necks/heads. It is a birthmark and nothing to worry about and will fade over time on it's own. If you are still concerned please have a pediatrician evaluate it before subjecting your baby to unnecessary and potentially harmful tx.
Why ? If this is what I think it is, a birthmark called a stork bite, it is benign and should be left alone. You doc could confirm it. If you are obsessed over it, it would likely respond to laser therapy, but that is a significant investment in time and effort. The kid would require anesthesia during what could require several separate treatments.