When something small and abrasive get in your eye -- such as a piece of sand or dirt whipped up by the wind -- for heaven's sakes, don't rub your eyeball. That's its downfall! Go to the kitchen and chop up small bits of onion (we call it mincing) -- and let your natural tear wash away that intrusive speck.
If your onion tears alone do not flush out that thing in your eye, grab a facial tissue. (Or bathroom stationery: whichever you get to first.)
With one hand, pull your lashes so that the upper lid is away from your eye. With the other hand holding the tissue, blow your nose three times. The pressure should make that foreign "visitor" take a powder.