"hypocondriac" was on to something that I have behind my ear as well, the only difference is that mine doesn't look or feel like a pimple.
When I first noticed it, it was very small but now it is about 1/2 inch long and it runs in the crease behind my ear just behind my earlobe, it is skwooshy, like a blister.
It doesn't have a head on it, there isn't any indication of a bite and I'm kind of freaking out. When I first got it and noticed it I would touch it to see what it was and when I did it would hurt really bad, down to like the middle of my ear (inside). Now thaat its bigger it doesn't hurt as much, and also doesn't go all the way into my ear now.

Does anyone have any idea what it could be.