You trained Nezha. Now his a heavenly deity and his became one of the three members of the Celestial Court. And a big job protecting the Jade emperor of Heaven but honestly, he doesn't really care about his duty he only cares about you his Master, his supposed to serve you not him but as Goddess of the Stars your duty is to protect the Universe. When you were training Nezha a Demon named Lady bone Demon attacked the world trying to kill thousands of humans and it's you're job to protect them.