I know a lot will say cull it - it is probably a cockerel anyway!! I have had chicks and hens with damaged legs, including broken, and they have recovered. Usually have a bit of a limp, but no detriment to their egg laying ability. You could make a little splint, but its keeping a chick still, although they do stand under the hen, so it could do it.
I assume you have now made sure the hens cannot reach any more chicks., Our farm cats are always putting their paw through the netting to try and get the chicks.