Is this the same pair that just laid another egg? If so, you need to discard the eggs. And as soon as the younger chick has left the nest box, take it down. They really do not need to be going in and out. The parents can still feed them when they leave the box. Don’t force the little one to leave, but once it leaves, remove the box so it won’t go back and so the parents won’t nest again right away. If the hen starts another clutch, she may stop feeding the chicks and let them starve.
Is the chick that went back in weaned yet? Sometimes you get a chick that wants to be babied. This can happen when handfeeding also. Some just want more time to be hand fed. It’s OK, as long as it isn’t hurting the little one. If you think it is, then you may need to move it to another cage. But if it isn’t weaned, this won’t work. It may be scared by something outside of the cage. The cage should be in a private area where they don’t see people and other pets. If you think something is scaring the chick, place a light cover over one end of the cage, and have a perch there. This will make a nice little hide where the chick can sit and feel safe. As long as it is eating, or being fed by the parents and seems active and bright, I wouldn’t worry. If it seems lethargic, sleepy, eyes are dull, feathers fluffed up – these can be signs that something is wrong and you would need to take it to an Avian Vet.
Thank you for asking Lafeber,