Persistent 7/10 left shoulder blade pain after coughing hard. 21 days recovered from covid-19. blood clots? stroke??

That is rather suggesting a musculoskeletal source (strain/ radiculopathy) following severe cough spells, other sources for the pain cannot be ruled out, they are less likely. It would be prudent to follow up in the office with your family doc for a focused exam and tests as needed.

Stroke is highly unlikely. Coughing may be straining the muscles. You may take acetaminophen, no more than 4 g in a day, no alcohol. Start exercising at an intensity that you can tolerate and gradually increase the rigor or exercise. Raising core body temperature through exercise will improve muscle health and relive the symptoms. Wish you good health!