I've been struggling after a COVID infection about 15 days ago. During the infection, I had a hard time breathing and it felt like something was stuck in the center of my rib cage, making my oxygen levels drop to 90. I had an HRCT of 1025 and have since recovered, but I still can't take a deep breath. When I do pranayama, I don't feel pain in the center of my chest when I breathe from my right nostril, but I do from my left, and my breaths feel shorter on that side. For the past week, I've had constant phlegm in my throat that just won't come out. My oxygen levels vary from 98 when sitting upright, to 95 when relaxed, and between 93 and 92 when lying down. If I manage to get the phlegm out, my oxygen goes back up to 98. I'm worried that my levels might drop more when I sleep. What could be causing this pain and how long could it take to go away? I've been sleeping in a prone position since COVID started and I'm constantly checking my SpO2. Can you help me figure out what's going on with this chest obstruction and the phlegm in my throat?