Dr. B called me back. When I described the situation with the swelling returning this week after cantering, he said "Just roll with it. Keep going. That x-ray looked too good for me to be worried about a little fluid. Keep rollin', but go slow." He said using anti-inflammatory cream was a good idea, and to go with that if I get more fluid in the area. He also said to let him know if the swelling doesn't go away after work, and to keep him informed regardless.
Okay, I'll keep going. We'll see how Kaswyn is tomorrow. I'm hoping for less fluid and no lameness.