Is there any guinea pig expert or a guinea pig owner could tell me what going on inside my Baby guinea pig eye, like there's this white thing growing INSIDE the eye...

A cloudy eye may indicate an ulcer, something that can result from a small piece of hay in the eye. Any eye problems require urgent veterinary attention. NOTE: Guinea pigs secrete a milky discharge from their eyes, applying it to their paws when grooming. So if you see this, it's nothing to worry about.