Pain in lower chest still there, after recovering from pneumonia?

Needs evaluation. This kind of problem needs a medical evaluation, it can be something as simple as a sore chest muscle from repetitive coughing, to a persistent infection in the space between the lung and chest wall ( the pleural space) called and empyema, which is potentially serious. Other causes exist as well.
Possible. Check for complication like parapneumonic effusion, so hard to say pt recovered.