I live in Canada. I lift up my two year old and hear a crack. then he would not move that arm. I took him to the walk in clinic. There is no need to go to emergency at the hospital. I am not sure about the US. I waited 5 minutes top and the doctor just move around his arm and fix it in a few seconds. Then he asked me to take him out walk around for 15 minutes and try to encourage him to reach higher and see if there is a problem. If there is I go back. All good. It happened twice to our boy and we went to the same walk in clinic twice. No biggie. Nothing to worry about.