I am so sorry to hear about your nephew. Bullying is a horrible thing and must be firmly opposed and corrected. It is, however, not a simple matter of one child going out of control, but often involves chronic issues involving the child, his/her family and the school.
I am supposing here that the school has been notified and that proper procedures are in place to hold the bully accountable. I also pray that your nephew has recourse to counselling and therapy if necessary. Bullying often can have lasting damage to self worth and may severely impede one’s social skills.
Meanwhile, we must pray for your nephew’s healing and protection, as well as the conversion of the bully and whatever may be wrong with his or her family environment.
A search on the internet did turn up a number of saints related to these intentions. I will leave it to you to explore. Here are some of the more well known saints that could help:
- St. Joseph the Patriarch
He was bullied by his older brothers and were sold to Egypt. However, despite this great harm done to him, he was preserved from evil against his brothers, but rather returned good to them and achieved great good for many. Pray to him to intercede that your nephew may also be protected from further bullying, and especially protected from returning evil for evil, but rather developing a greater love and trust in God. - St. Joseph, Husband of Mary
He was of course entrusted to protect Mary and Jesus. He is a great intercessor for divine providence and protection. - St. Jude Thaddeus, apostle
He is one of the Twelve and is the patron saint for impossible causes. Pray to him for the conversion of the bully. - St. Rita of Cascia
She is also a patron saint of impossible causes, especially for desperate family situations. Pray to her for obtaining the graces necessary for whatever family situation that precipitated this kid to become a bully.