I take the word lung infection as respiratory tract infection. viral respiratory tract infection are known to produce generalised involvement of whole of respiratory tract mainly nose, throat, larynx and trachea. after such an infection there will be decreased ventilation of ear due to involvement of eustachian tube which connects ear to back of the nose. this will cause mild pain and blocking sensation in ear. usually this condition is self resolving. if it continues to trouble you then consider taking anti cold medicines or consult nearby ENT specialist