Thanks for your question on Health Care Magic. I can understand your concern. Your doctor is right about fibrosis. In pleural effusion, after healing pleural surface becomes thickened and fibrosis. These surfaces lost its smooth texture and thus on friction can cause pain. So pain on effusion site is common after treatment for pleural effusion. Pain is more common when pleural surfaces rub against each other like while coughing, sneezing, laughing, yawning etc. This is normal thing and you should not worry much for this. You can apply warm water pad for pain relief. Or you can take painkiller drugs if pain is discomforting. But better not to take anything. Hope I have solved your query. Wish you good health. Thanks.