When photographing an unfamiliar object, place a ruler or a familiar object next to it, such as a coin, so we have some idea of its size. I'm viewing this thing as being six inches long, but I'm guessing it may be closer to an inch. So, tell us the size, please.
It most likely formed in the oviduct when a tiny bit of tissue sloughed off and traveled down as a yolk would, gathering albumen and membrane along the way. It's nothing to be worried about, and it is almost always a one-off event.