This just started today, but-

I was eating a granola bar, and bit down as I always do. It sent a lancing pain through left eye and into the area right above my eyebrow. It hurt very badly and caused my left eye to water. Any idea what this could be? I could really use some input! (I ate yakisoba later, and the same thing happened, so I don't think it had anything to do with the hardness of the granola bar. Also, it didn't hurt constantly, it was only every couple of bites.)