Sunnah on licking fingers after eating

We know it is sunnah to lick fingers after eating a dish, what if one had the thought and sunnah in his mind, about to lick fingers but after eating he was not able to do it as his mother had called him. He had the knowledge of sunnah in his mind but due to some reasons he was not able to perform it. Is this kufr? He hadn't intended to reject sunnah or perform kufr.