Sadly you do have a damaged screen.
Often a blow to the lid can cause problems as the damage is hidden. You can prove this to your self by using an external display. If it shows a good image then you know it's the display.
Here is the IFIXIT guide you'll need to follow to fix this on your own: [guide|40753|MacBook Air 13" Early 2015 Display Assembly Replacement], and here is the needed part: [product|IF188-096|MacBook Air 13" (Mid 2013 through Early 2015) Display Assembly]. As long as you have the correct tools and patience this is not that difficult a job to do.