Q. A young lady brought her 4-year-old son to the emergency department with an inability to move his right upper extremity. The mother mentions that four hours ago, while she was putting on his clothes and pulling his right arm into the sleeve, he cried, and since after, he has kept his right upper extremity in his side and does not move it. As the mother reports, he had no trauma incident and no significant medical history other than the usual childhood viral diseases. His vaccination is up to date, and he has no previous fractures. He is a calm, sweet, and cooperative boy on physical examination. His vital signs are normal, just a slight tachycardia (pulse rate is 105/min). He is holding his right upper extremity beside his body in slight elbow flexion and denies moving it. There is no swelling around the elbow. Gentle palpation reveals no tenderness around the elbow. Gentle passive motion of the elbow is not painful. Neurovascular examination of the limb is intact. Other physical exams are normal. What is the best plan for him?