Took a closer look at it, and it seems like it's a small hair in his eye (the size of a human eyelash), and it's like there's an infection around this small hair, somewhat like mucus as stated. As much as I want to take it out, I don't feel comfortable doing it.
I have an appointment tomorrow evening, they should be able to take care of it I assume, but until then, is it bad if I leave it like that? Cat is an indoor cat, has no symptoms or anything, as exited as before, doesn't have problems seeing, almost seems like the cat doesn't care about it...
Thanks all for the inputs,