It is hard to know exactly what is going on without seeing Nicky. If he is squinting and closing his eye more than normal, I would probably take him back to the veterinarian to be examined. Some cats can be carriers of the feline herpes virus and this virus can cause a little bit of squinting or eye irritation without any other signs. The symptoms tend to come and go and may need to be treated on occasion when a flare-up is severe. Feline herpes virus is usually diagnosed based on clinical signs and a good eye exam can also give some clues. In most cats, this is not a serious disease and if Nicky is a carrier he should be fine. Let me know if you have any more questions after your visit to the veterinarian.
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I adopted my cat Nicky a year and a half ago (he is now two years old). He has always 
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