HI Vickrant Shinde,
As Marius van der Knaap mentioned, The Cover Photo Object is empty . All the association and read/Write access you have given is correct. But when you are showing the Course page , the Course_CoverPhoto is empty .
You can make it Editable in many ways
Most likely the image object is still empty, that's why it appears as non-editable. Make sure to create a CoverPhoto entity and associate it to the Course object, for example on creation of the Course object.
Give the association Course_CoverPhoto as Read, write not just Read. Also create object for CoverPhoto