^This^
The yolk should shrink within the next 48 hours if not you will have to cut it off (ask for advice when if this is the case)
I will also touch on this
In my experience cutting (sometimes too early) and messing with the eggs (checking on them) once cut will lead to tangled umbilicus. Tangles umbilicus are RARE the fact that you experienced this several times being new is not normal.This is our first clutch of eggs to hatch and have already lost several to twisted umbilical cords and hard yolks.