In-homogeneous opacity in the left lower lobe means to say that there is opacity in the left lower lung but it is not uniform, it is scattered in appearance.
Opacities in the lung is seen in active infections. It is a common finding in most paediatric respiratory cases.
Your son may be having an acute lower respiratory tract
infection as he had fever
He may require a course of antibiotics like amoxicillin
for a few days. Discuss about this with his paediatrician.
The finding on the chest X-ray will resolve soon and become normal.
Give him steam inhalation thrice a day to clear the secretions in the airway.
Do not worry, he shall be fine soon.