That's actually sugar syrup that has seeped out during the cooking. It's quite typical to see beading on more rustic, country style pies and it does not bother me in the least. If you insist on having a perfect meringue with no sugar beads on top, you'll need to try something like an Italian meringue that requires more steps and is stabilized to prevent beading. I kinda like the little beads myself :-)