It's a tiny bit of yolk sac that didn't absorb. That part will most likely shrivel up and fall off. I had one that had a good amount of yolk unabsorbed. Almost all except a little bit like that absorbed. That little ball dried up and pulled up against the chick. A couple days later I was examining it to see if I could get under it to cut it off and it fell right off.Nope, was not shaking, thankfully. Got a couple more pips 8-0 gonna be another long day. and working on an MHP upgrade....finally going to pad under rack. Got one chick with an umbilical bump, at about 24 hours old it looks like it's drying up. Thought maybe @AmyLynn2374 could take a look, I know she has beaucoup hatching experience. Will tag her here but maybe I should PM? I left this one in the bator , thought the moist environment would be better??