Now, that is odd.
I had to go pull out a stock battery for a 510 (I hardly use them anymore, use mods).
I can't tell much by your picture, but my guess is it was something out of your charger (or PCC maybe?) that came loose with it the last time you charged your battery?
Might want to get a back up charger (it is good to have a few around, just in case). A USB charger is cheap (and comes in handy with a USB plug adapter in your car for emergency charging).
If it is new, contact your supplier? Check to see what their warranty period is first... not much to do about it if it is out of warranty.
I'd keep an eye on it. If you don't see any difference in that and your other
batteries under magnification, and everything continues to charge ok, I wouldn't worry about it.