Could The Pneumonia And Partially Collapsed Lungs In A Toddler Be Related To A Past COVID Infection?

My 2yr old son has had a bad chest, cough and runny nose on and off for a year. We finally got in to an appointment with a doctor and it turns out he has pneumonia and partially collapsed lungs. His white blood cell count is showing in blood tests as normal not high. I very worried what has or is causing this we had covid just before his 1st birthday could this have been the cause or is it likely to be some kind of underlining disease?