My foot is just killing me. Can anyone help?

What's going on is, I think the problem started at my last training session. I was standing on one leg, on a sort of bench thing, and lowering myself to just touch the ground with my other leg. It was VERY hard. My trainer said she heard something go POP loudly but I didn't hear anything or feel anything, so we went on. I didn't feel a thing until the next morning.

Unfortunately, the next morning I could hardly walk. My right foot is absurdly tender in one particular spot, sort of the right side of my heel. I've had problems with my hamstrings before, but that's right in the back of my heel. This is differently placed, and the pain is different. It's a bad pain that makes me feel a little sick and it doesn't go away with a bit of stretching the way hamstring pain does. And it's hard to stretch without aggravating it. I've been icing it and trying to stretch it a bit, but it totally sucks. I wanted to go hiking today but not so much. Has anyone had this problem?