I cannot give a clinical diagnosis over the internet
It is possible that if you had a sufficient force/turn to the neck when you fell, you may have torn or dissected a carotid artery where the fibers supplying the eye dilator muscle travel. This should be ruled out by MRI and/or dye angiography. It should still be possible to see a dissection at this point - if one is present the treatment at this point (3 months after) is just an antiplatelet agent like aspirin - it heals spontaneously. The risk for the artery to be blocked or break off blood clots and cause a stroke is greatest in the first few weeks, after this any clot organises and heals up.
Its also possible that the fall was conincidental and it is due to another cause - this should be followed with your neurologist
Good luck