Extraction Concern?

[Gracep98]

I got my wisdom teeth extracted yesterday, and today I was eating some soft food (apple sauce) and I thought that a piece of something had gotten into my teeth. I quickly and gently wiped my tongue across the side of my gums when a huge piece of dead gum (at least I assume it was dead, it was nearing the color black) came off. It ripped out and I started bleeding, and the flap began right around where one of my extracted teeth were. I'm very worried that I may have accidentally taken off something that wasn't meant to be removed, as it also had something that looked like plastic floss which I imagine was some stitching. The flap of gum was extremely long, spanning from the back of my mouth all the way to my front teeth and then broke off. Is this a big concern? If its completely normal I'd rather save the money in going back to the surgeon two days after my extraction, although I'm concerned about dry sockets. Thank you for your time!