Help! What do I do with this bird?

There is a phoebe bird nest in the top corner of the cieling of my back porch. This morning I found a baby bird that had fallen out and was trying to fly away but couldn’t. My mom put it back in the nest, but it fell out again that afternoon. It’s fur is all ruffled and it looks like his left foot is broken. I tried to give him a meal worm but he would not do anything, even when it touched him. What can I do to help it?! Please help!