I found a photo similar to what I'm seeing here with mine.
http://img228.imageshack.us/img228/7880/img3243o.jpg (Not my photo)

Basically my garter has the same thing except it's far less conspicuous. It's also not as concave, has absolutely no discoloration, and its more of a tiny indentation then a fold like in this pic.

So in general what my snake has is a similar thing but it is much, much smaller. It looks a lot worse in the picture of the python than what my garter has.