Awe, Jim, how wonderful of you to save the little bird.
I've seen an injure bird or two and very often they do heal, sometimes miraculously! Do you know where the parents are? If possible, you might try to put it outside, out of reach of predators. Once it's strong enough, it will fly away.
Hopefullly someone else will know better what to do and how to care for the little bird until its healed.