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.
Hopefully just a glitch.
How old is this bird, in months, and how long has she been laying?
Where in this world are you located?
Climate, and time of year, is almost always a factor.
Please add your general geographical location to your profile.
It's easy to do, and then it's always there!