If that was my wound, I would need a medical professional to keep slapping my hand away when I started tugging at the loose ends......
I think that blue thing is a drain, designed to vent Evil Fluids away from the flap wound so that the flap sticks and lives.
If blood and goo accumulate under a flap, it can Slough Off and Die.
Once a wound oozes less and the flap looks a Healthy Pink cf a Dusky Blue, the drain can be Pulled Out with ouchiness.
If the flap turns Black, a skin graft might be needed.