Will a 3 mm echogenic focus possibly reflecting a nonobstructive left renal calculus without hydronephrosis cause kidney damage? will this pass or is intervention required?

This should be assessed and explained by someone who has the films to look at along with the report. A tiny stone located within the body of the kidney can sit there forever without complications. Stones become a problem if they form in the collecting system and block urine exit, creating backup pressure. An evaluation looking for why you formed a stone would be reasonable.

No it will not. The smaller the stone the higher the chances of passage- this has a high chance. But it also depends on the anatomy of the kidney and the position of the stone in it. Drink a lot of water. good luck