How to help this hatch-ling (chick) live?

My pet chicken had her first eggs and 2 out of 7 hatched today. My mom thought that the mother chicken abandoned the eggs since she left to feed her newborns for a little bit so she took the nest out and left it outside. I wasn't home so I didn't know until I got back and I found one of the eggs half hatched and the chick crying helplessly. I put the nest back in and the mom tried to warm it. It was still partly in the egg and looked okay but what can I do to ensure that it will live? I don't like to see babies die when they have their whole life ahead of them so I want to help anyway I can. Please, any ideas? Or is he better just left alone with his mom until he fluffs into a healthy chick like his two siblings?