im trying to sue the person that stabbed my son

If your son is alive, only your son may sue.  If he was killed, you might sue for wrongful death under certain circumstances.  If your son is a minor, you must petition the court with jurisdiction over the case to be appointed a special guardian for your son to bring the lawsuit for his benefit; this is called a "Guardian ad litem."  You may sue for your own expenses such as medical bills.  Good luck.