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I'm sorry to hear about your cat‘s eye. What you want to watch for are signs of rubbing at it, reddening, discharge or cloudiness appear in the eye.
You should rinse the eye with sterile saline, like that found in regular contact lens solution, (not the ones with disinfectant but just normal saline/ NaCl) and do not let the tip of the container touch the eye. You can wipe around the eye with the saline soaked on a soft cotton ball or gauze, but don't use anything harsh like paper towels. It's possible some debris or dust or litter got into that eye, causing some irritation.
If you should start to see any discharge, then you can also find an ophthalmic antibiotic ointment at a pharmacy: like terramycin, triple antibiotic (neo/poly/bac), etc. Ask the sales people if you need help, but it does need to be safe for the eye, not a topical one for skin. After rinsing the eye, apply the ointment 3 times a day (every 8 hrs) for 10 to 14 days.
It could also be a scratch or ulcer forming and if the squinting continues or if discharge starts but doesn't start clearing up in a couple of days, you'll need a vet to check it.
Best of luck, and let me know if I can help further.