Awww, so sad !!
At this point you have to decide whats best for the chick !!!
We/us as animal owners need to make the best decion and not let our animals suffer. I know its hard, b/c we think just maybe it will be ok or what if it I cull and it would of been ok !!
But, at this point you know the chick is in pain and you have no clue how to treat or even if it can be treated. So I would say go ahead and cull to help the little one out.
Unless you know for 100% sure the chick is going to get better !!
I asked hubby a few weeks back why our sickly/old hen wouldnt die on her own, I mean she should of been dead weeks ago but was holding on for some reason, he replyed back somtimes animals hold on for reasons and just need a little help moving on !! She ended up getting real bad over the next week and he culled.
As far as how to do it is up to you, is there anyone that could do it for you ?? I wish I could send hubby to you so he could do it for you !!! I guess if you CANT do it and CANT find anyone to help you, you could pay the vet to put it down for you (not what most would do, but would get the job done if you cant) Good luck