The lunar near side is not shielded from impact craters in any significant way. Impactors can cross the earth's orbit and hit the near side of the moon just as easily as they can hit the far side.

The fact that the near side appears to have large areas with few craters, and the far side doesn't, is a result of many near-side craters having been erased by lava flows. It's not because it received fewer impacts.