If the muscle is just sore, then a short, easy paced recovery ride would be fine. From what I've heard (and I think there was a thread on here about it recently), it's good to get a little blood flow back into the muscles; it will help flush out the lactic acid faster than if you just rest.

However, if the muscle is actually pulled then resting/icing might be a better idea. You say "it felt better this morning" from which I infer that it was painful last night after the class. If it was just regular soreness, then I'd expect it to hurt more today and tomorrow than it did last night. Sounds like you might have a minor pull; probably best to play it safe and give it a few days rest.