It's some kind of pigeon. I'm afraid the prognosis is probably poor. If you don't have a wildlife rescue near you that you can call for advice, then it's probably best to put it in as safe a place as you can outside and leave it to fend for yourself.
Pigeons breed year round. It's why they're so numerous. This doesn't look like a fledgling though. It may have flown into a window. Sometimes they recover. Sometimes they don't.