Do regular chest physiotherapy and also consult a chest physician. Provide him.to best massage for chest

He should consult a Respiratory Physician to rule out that there is no recurrence of lung infection as early as possible. If everything is normal then he can do breathing exercises with proper guidance.

Heat coconut oil and massage that area gently twice a day.....do breathing exercise......

Hello Dear! happy to know about your father's recovery from covid. due to the pneumonia that develops because of corona the intercostal muscles get tender and inflamed. if there is no  reason evaluated by physician then start with hot fomentation on the pain area for few days the symptoms will subside and practice deep breathing exercises and let me know after 3 days

Hi happy to c your father recover .the left side rib pain can be of any origin need to do proper evaluation from msk n cvs point of view

Do hot fomentation over the painful area.....

Happy to hear about your father's recovery.....after chest infection it's common to having chest pain. It can be because of costochondritis(inflammation of cartilage in rib cage) or may be intercostol muscle pain, Tell him to do some breathing exercises & apply hot water fermentation on affected area. Still don't feel relief then immediate consult with chest physician....

He needs to get examined properly. Without examination it would be difficult to suggest what can be the cause. There are possibilities of a persisting infection still. Once you are sure that everything is sorted and still pain persist then it can be muscular pain and deep breathing exercises can help.