It is common to have chest congestion and an occasional cough for several weeks after a chest infection, even after treatment. This usually happens because the airways remain sensitive and mildly inflamed even after the infection has cleared. In many cases, the lungs continue to produce excess mucus during healing, leading to white phlegm and coughing. Other possible causes include post-nasal drip from the nose or sinuses, mild airway irritation after infection, or acid reflux irritating the throat. Since your phlegm is white and there is no mention of fever, it is less likely to be a new bacterial infection. You can support recovery by drinking plenty of warm fluids, doing steam inhalation, and avoiding dust, smoke, and cold air. Eating light meals and avoiding spicy or oily foods may also help. Rest and good nutrition also aid healing. If your symptoms last more than a few weeks or if you develop fever, breathlessness, chest pain, or yellow-green phlegm, please consult your doctor again for further evaluation.