By now the injury must have been dealt already and overtime its already cured. If its not the fist that's broken, it wouldn't be a big deal in the fight. Inoue is not old yet, there is no way he can't get used to the weight after few months.
One more advantage with this fight is that Fulton vs Inoue fight will be held in Japan. He'll do his best to impress his fellow country men to give them an spectacular KO.