Hello,
Graft rejection is a dreaded complication of corneal graft - in a few severe cases, the graft just can't be saved.
The most commonly performed course of action would be to commense steroid treatment & later try a repeat graft.
As long as your retina is fine, the cornea can be regrafted to improve your vision.
Next Steps
As of now just follow your doctors advice.
If you have had keratoconus prior to surgery - don't rub your eyes