Yes it is unusual. Swelling of the eye and cheekbone are totally different from headaches, eye strain or discomfort due to the eyes not working together after one eye is "fixed".
By 16 weeks all swelling should be gone. One thing you might consider. After cataract surgery people see better and often notice things that were there before surgery but didn't notice because of cataract reduced vision. Thus it is almost weekly that people after cataract surgery notice wrinkles, grey hair, dust around house, different colors to their home and ward-robe. Some notice "swelling" that are really age bags that were their before and often are on both eyes.
If you are really concerned and not satisfied with the surgeons explanation you can always seek a second opinion
JCH MD
The swelling is not there all the time. But at times it is unbearable. I have been told it is an allergy, light shining on the cornea and even that it is impossible. Now wearing contact lens in good eye, to balance them problem still persists
Suggest you seek a second or third opinion as this is not normal and the explanation you're working with doesn't make sense. Hopefully opportunity exists for you to see a private consultant or a different group of ophthalmologists within the NHS service.
JCH MD