Hand foot and mouth?

Hi, my son is 3 years old. I noticed during his baths recently that he has a lot of extremely raised bumps on his back. All over. They don’t itch or hurt him. They’re literally only on his back I’m gonna make an appointment but until then what does this look like? I’ve been washing him and keeping it moisturized thinking it’d go away but nothing has changed. It’s just weird how they randomly appeared but don’t seem to bother him.