OUCH!! It definitely hurts them, because my lead hen broke a nail (not ALL the way up like yours) last year and limped around for two days. I did clip it off, because I figured it'd snag on something and bleed worse. And it will bleed more when you clip it - corn starch can help stop the blood. Blue Kote is good. I babied my girl for a day, kept her apart more so that she didn't get dirt and such shoved up in there, but I have no doubt she would have done fine if I'd just treated it and let her go...