That should be treated by a vet its very easy to kill a bird trimming its beak and thats assuming th quick is where it is supposed to be which in this case i doubt it is.
From the picture the quick looks like it is where it should be.
I'd only nip a 32nd or 16 at must at a time & give it something to grind it on. Maybe glue sandpaper in the bottom of the feed dish & only put in small amounts of feed so it has to rub the bottom of the pan.