Wrist pain before 10-miler

Possibly just posting because I am panicking slightly. Two days ago, I got a pain at the base of my thumb/top of my wrist that seems to be getting worse. I've stayed out of the water, been popping anti-inflammatories, and today, bought a hand stabilizing thing at the Pharmacy, just to keep me from using it. Despite it, it feels like there is one spot that is just killing me. It's at the joint at the very base of my thumb. So painful. The bummer is that I am doing the Kingdom Swim 10-miler on Saturday. Any thoughts? Anyone ever swam with a wrist brace of any kind? I'm trying to just not use it, but frankly, am worried about around mile 6 or so...