What everyone else says in logical. If it really hurts, go see a doctor. However:
I got my wrist *really* wrenched during a nikkyo, a wrist which was, like yours, just recently hurt by a bad break fall from a shihonage.
I practiced the next day, and it still hurt. So I taped my wrist with hockey tape, to show people it was hurt. I practiced lightly on that side, and, with time, the pain went away.
So - my advice in regards to this is - take a week off class and see if you can save yourself $75 if it feels "ok" after that. If not, tape it up, and continue practicing on the other side, avoiding the hurt side, and see if it feels better. If it hasn't noticeable improved by that point, give in, and do that doctor thing.
I sympathize about the money issue - I'm saving for New York Aikikai Summer Camp, which means for groceries and going out, I can only spend $20 a week. The above, though, should at least not aggravate the injury, and gives it time to turn out to be "nothing."
Good luck and good healing!