I will recommend physiogel as it is recommended by my doctor for its effectiveness in locking moisture after application which is great for sensitive and dry skin too. My baby had been using it till now he is 2yrs old.
Looks like dry chapped skin behind the ears, which is common for babies -- I suggest a light layer of vaseline jelly or any light baby moisturising cream, it should clear up in a few days.
You can try applying some baby oil on the area after bath. Just a thin layer will do. :)
My baby has this too and I apply physiogel or papaw cream on it.
u can try use vaseline jelly.. apply a thin layer on it
Use moisturizer