त्वाम् to you, विनिहतात्मानम् who has killed his soul( one who acts against his conscience), धर्मध्वजम् functioning under the banner of (showing off) virtue, अधार्मिकम् unrighteous, पापसमाचारम् sinful in conduct, तृणैः by grass, आवृतम् covered, कूपम् इव like a well, न जाने I did not know

'I did not know that you have killed your soul (by acting against your conscience), that you are sinful in conduct and unrighteous under the show of virtues like a well, its mouth covered with grass.