Well, the child might need a pair of glasses if he likes to squint. The action can indicate the presence of a refractive error, which affects ability the of the eyes to focus on an image. Squinting can bring objects into focus but only temporarily.
I remember that I used to rub my eyes a lot when I started to get nearsighted. My eye doctor told me that it could cause eyestrain or fatigue. So if your kid also like to rub your eyes, he or she might have eye issues and glasses might be necessary.