Hello! My son has been sick for two weeks now, and a week with a wet c…

Hello! My son has been sick for two weeks now, and a week with a wet cough. We saw a doctor and he diagnosed it as pneumonia. We're treating it, but yesterday closer to night, a whistling sound started. I wanted to observe and call an ambulance in the morning, but the whistling sound is gone now. Should I worry and still call an ambulance?