If the yoke sack broke you wouldn't have a dry cord and you would see it . What your looking at is just excess fluid that is around the chick . And for some reason I can't ever spell what it's called . I can butcher a word so bad my spell check throws up a white flag .

. Whenever the cord is dry like that and still stuck to the shell I use my fingernails to pinch it into . It takes a few days for it to heal completely. Like Pyxis said wash it's butt and feed it. Not only has she hatched many many chicks she hatches all kinds of other fowl too . She is a just awesome . I just like to butt in . I think your all good .good luck with your hatchlings