Dry patch on my sons head (4 week old)

No matter how much oil or lotion I put on it won’t go away. I like to rub my fingers across his head to put him to sleep when he’s tired but I can’t do that because his dry skin rubs off with it. I noticed it when I took him out the bath last week and was getting ready to put lotion on him. What are y’all’s recommendations? I’m about to call his pediatrician and ask about it.

TIA!