First of all the bad news. If you can, put it back in the nest with mom. There is a likelihood she pushed it out. Here in KY, that is the extent of legal human intervention.
It is more legal to shoot doves (with a license, during season) than to "save" a chick. The logic makes sense in a cold, survival of the fittest way. Intervening means you are taking away from that mother dove the decision about whether the baby is worthy of raising. There may be genetic or anatomical problems that aren't apparent to us.
If for some reason you intervene, keep mum and try to find a licensed rehabilitator to take the bird to. Doves feed their young crop milk. In the near term you can try a runny, warm mash of chicken feed (NOT layer ration),maybe adding a little egg. Rehabbers use a lot of parrot starter, like Kaytee Exact. It is pricey stuff, but a good thing to have around for sick chickens sometimes.