DISCLAIMER: this post is nothing except a reminder to myself. I'm not a doctor in any way lol, I'm just listing things that help me with wrist pain.
So, I don't have any conditions, but I find myself easier to get sore hands even from slight overworking lately, and it prevents me from drawing for a week or two at worst. Again, not that much, but still is annoying, and some measures should be done.
So the first thing I should do is to do more exercises for alleviating pain, mainly these two that help me the most:
(wrist extension, click for source)
(wrist flexion, click for source)
The second thing I should do is to consider using a Joystick / Gamepad with On-Screen Keyboard if it gets really bad, and I can't use a mouse. Not everyone benefits from that, but for me, using a Gamepad was always easier to my hands, if that's also your case, I'd recommend using AntimicroX that is available on Linux and Windows.
AntimicroX supports even those shitty cheap gamepads, so give it a try!
The third and still an important thing to remember is DO NOT DRAW IF IT'S STILL SORE. Even if it's very mild, if you give up on your patience you're practically going to reset your await because the hands will get worse. Please just wait it out, do other things that don't require hands to use, as an artist who has hands itching from not drawing I know it's very hard but your physical health should be the priority. Inform your commissioners that you're not able to do work for a certain amount of time, they will understand.
Hope this really short post helps!