Deep breath issue, low spo2 when relaxed

Hello sir my age 37, I’ve been COVID positive 15 days back, during Covid I got breathing difficulty like something is stuck in Center of rib cag due to which spo2 went till 90. Hrct- 10/25 I got recovered 15 days back still deep breath is not possible, also when I do pranayam , I do not feel that Center chest pain pain when deep breath from right nostril but felt left nostril and breath is also short when using left. From a week constant phelgem in throat which doesn’t comes out, my spo2 in upright position is 98, in a relaxed position it’s 95 and supine position it’s 93-92. When I suck the phelgem, my spo2 increases to 98. In sleep it might be less. What it could be which is causing pain and how much days it’ll take to go away, I slept in prone position in Covid and sleeping till now. Always kept on checking spo2 Please help me to recover form this chest obstruction and phelgem in throat.