It happens all the time in fiction, but it's probably not realistic for a human-sized person to just "push away" a meteor. At least not without the ability to sustain flight. I'd imagine applying the amount of force necessary to rapidly overcome that giant meteor's momentum, via the tiny surface area of Saitama's hands, would be about as effective as trying to stop a speeding car with a bullet. Regardless of whether his hands are closed into a fist or not.