What could this rash on my baby's face be?

I know the age of my child shouldn't matter but he is 2 months old and hasn't had any problems until now. This past week, a really dry patch of skin showed up on the side of his head, the pediatrician said it was cradle cap and gave me lotion to care for it and said it probably won't get any worse. He also got shots on Tuesday and I don't know if this is some kind of reaction from that, but he has bright red rashes all over his face.. They are especially on his cheeks. I know it isn't baby acne, and it looks like bumpy sunburn… What could this be? I am freaking out. should I call the pediatrician?