I think it's better off with the peahen unless you think there is an injury that needs to be treated or if the peahen is abandoning it. Even if it needs to be treated in some way, hopefully you can put it back with her straight away.
How old is the peachick? Is she leaving it alone on the ground or is she coming down to it? Does she have other peachicks? How long ago did it happen?
Can you observe a bit more and give more detail about what might be wrong with the peachick so you can get help deciding what to do? For example, do you think it has an injury or is it just a bit stunned?
