My convict cichlid fish is going to die.help!!?

[Bobby]

my jewl cichlid attacked the convict , i thing he bit his fin off because the convict cant move and always is laying on its left side on the top of the tank. this means he cant eat either, is this the end for him. would it be better if i put it out of its suffering or let nature do it.Can his fins heal,the jewl dosent attack the convict any more