Newton may have been rough/arrogant with other people, but this is entirely consistent with being humble in the face of the mysteries of the universe etc — there is nothing in his biography to suggest otherwise.
In fact, you can see hints of it even in this quote: “I don’t know what I may seem to the world” — suggests that he thinks of himself in an exalted position wrt the world (= other people, in this context), but a little boy wrt Nature. Something like: I am a little boy collecting pebbles on the shore, while everyone else is a senseless baby not even close to the ocean.
In fact, you can see hints of it even in this quote: “I don’t know what I may seem to the world” — suggests that he thinks of himself in an exalted position wrt the world (= other people, in this context), but a little boy wrt Nature. Something like: I am a little boy collecting pebbles on the shore, while everyone else is a senseless baby not even close to the ocean.