If this does happen to your iPhone, resist the temptation to pick at the flaw or to pull it. Also, until you have the opportunity to bring the phone to an Apple Store or an authorized repair center, be extra cautious about exposing the device to water since the material unraveling could be related to the IP68 dust and water resistance of the phone.
Other suggestions mentioned by Redditors include the possibility that the phone is a fake, or that the phone was previously repaired and the new rear glass panel was installed incorrectly (this was denied by the owner).
Another post came from a Reddit user named “TheManchot” whose iPhone 15 Pro series unit suffered from the same problem. He wrote, “If yours is what mine was, do not pull at it. It’s the adhesive for the back glass (between the titanium frame and glass) and likely impacts IP68. I had an extremely small amount, and I used a very sharp, thin razor blade and slide it along the back – careful to not have the blade so vertical it would scratch or dig into the frame, but slice off the adhesive. It’s too bad that is coming out of the factory.”
