Great! Think you and your duck are very lucky! To post a pic, tap an open space like you are going to start a message. Look for the "Attach files" button. Should be near the Post Reply button, it is on my phone but may be different depending on your device. That should take you to your picture...
Please post pictures of the duck showing the injury, the eye and the entire head. And also please give a general idea of your location. How old is the duck? Sorry this has happened. Is the duck eating, drinking, moving, behaving normally? How long ago did this happen?