There is no universally accepted staging system for pleural effusion
on Xray. However, just blunting of costophrenic angles would qualify as mild pleural effusion (we use a classification system of mild, moderate and large pleural effusion at our institute).
It maybe advisable to get an ultrasound
scan of the chest done to confirm pleural effusion as pleural thickening may mimic effusion on Xray. Also, a USG guided aspiration and removal of the effusion can be attempted, either to determine the exact nature of the effusion or to relieve breathlessness if you have any. It maybe advisable to meet your chest physician and discuss this with your doctor.
Your blood counts appear normal, although the ESR
is a bit high. Overall, its probably a good idea for you to finish your antibiotic course and then repeat an Xray or USG.