Weird Looking Thing Near Tail

[AbsoluteApril]

I was handling my female baby (breeder said 2 months) BP today, and noticed that she's pretty fat around, and her tail is teeny. Then there was a scale or something that looked like it was open or something.

The larger scale where the opening is between the body and tail? Called the anal plate, the opening is the cloaca or vent. That is where they eliminate waste and facilitate sexual reproduction.
hopefully this link works:
https://goo.gl/images/Czi8PL
Not sure if that's what you meant