It is of concern.
That cloud possibly results a reactive condition (edema in the cornea) as a result of corneal injury (like a corneal ulcer that is trying to heal), or is secondary to some other eye trauma or infection.
Absolutely, that eyes needs to be seen by a vet,and sooner than later. Some of these inflammatory or infectious problems with the eye can progress quickly and can be painful.
Your vet may recommend a eye stain test: (link says dogs, but applicable to cats)
More info on cloudy eyes in cats: