Does sin befall the mother who refused to buy her son a silver ring, which led him to buy a silver necklace and another one of gold?

It is not permissible for a man to wear a necklace, whether it is a chain or a bracelet, as it involves imitating women, which is forbidden. Similarly, it is forbidden for men to wear gold, due to the saying of the Prophet, peace and blessings be upon him: "Indeed, these two are forbidden to the males of my Ummah." The sin is incurred by the one who wears it, not by the one who gifted it to him.