Haha dermatologist.. that's what I wanted to reply with.. but I actually have the 100% accurate answer for you, I was curious so I went to ask my friend who works in the seat department in the factory.
It's actually an error in the seat assembly line process. It's a metal wire called a "listing wire". It's what they used to affix the leather to the foam, it's not actually a bubble. It's the end of the wire so it's a loop, the anchor wasn't set properly. There's only been a few of these cases and have been warranted so you just have to bring it in and they will replace it for you. If you don't want to hassle with that, just push it back in, it wont hurt.
Larry