If you became a USC, you will have to call USCIS and let them know that you are then a USC. They will update the case and send you a letter if approved or denied. Usually what you will get is a NATIONAL VISA CENTER bill, or instructions how to apply for a VISA for your relative. That means the USCIS dept has already approved your case. May take about 2 months after you become a USC. Make sure you have your case # when you call USCIS so they update your I-130 form to USC I-130.