I'm really concerned because I had COVID about three months ago, and although Im better now, my chest still feels pretty heavy sometimes. At the beginning, my left hand felt numb, and I had palpitations, so I took Corbis 2.5 for about 10 days. The palpitations seem to be okay now, but the heaviness in my chest is still there, especially if I try to work out or lift heavy things. The intensity has decreased a bit, but it's still noticeable. I've had a bunch of tests like ECG, ECHO, D-dimer, CKMB, TNI, BNP, MYO, a chest X-ray, and PFT, all of which came back normal. Lately, Ive noticed that if I press on my chest, I hear a crackling sound like when you crack your knuckles. What could be causing this and what should I do about it?

That could be due to costochondritis,no need to worry take adequate rest and do breating excercises and also do use flexon tablet when you have severe pain