Pain because of this is very common and should be attended to when it first appears. Otherwise, inflammation and irritation and tension/guarding can lead to more serious troubles, like carpal tunnel syndrome.
When I first started my practice I was very enthusiastic about somatic healing, but I was holding unrealistic ideas. For this type of situation, I would have recommended that a person crawl about on their living room floor for at least five minutes a day. That would automatically stretch the palm back. I would also have recommended that they widen their palm, especially their thumb(s) as that hand was taking weight and the palm was getting stretched backwards by the weight of the body pressing upon it. In addition, using the hand and arm for weight-bearing in crawling on the floor activates a relaxation reflex in the palm and fingers (just as should happen with the feet as they take weight, they should lengthen and widen and soften and the ankle should be active). This would correct the problem in a short few weeks, and it was natural, it was what infants do (or should be allowed to do). The problem: nobody did it. Especially the older folks, the ones who needed it the most, would never do such a thing. So, either I had to give up my bright ideas, or modify them so anybody, of any age, could easily benefit. So here it is...
Part One: Bend the palm of the right hand backwards, as it would be if you did a push-up on the floor. Keeping the palm like that, bend the thumb backwards into a stretch, and hold the stretch position for about 2 or 3 seconds. Then release, pause a moment, and repeat for 10 repetitions. Please don't hold the stretch for more than 3 seconds; you'll get quicker results if you keep it to a more body-friendly rhythm. Cats, dogs and little kids all stretch for about 2-3 seconds, then it is over. Then the "stretch reflex" kicks in. If you hold the stretch longer than 3 seconds, you'll feel it is not quite the same nice feeling as it was at first. It is a good idea to also stretch all the fingers in a similar fashion, as well as the thumb and fingers of the other hand.
As you do this stretch, the "magic" happens if you also imagine your thumb or fingers, as you stretch them, are getting slightly longer, that they are lengthening. This involves more than just your ordinary idea of "relaxing". A definite mental resolve has to be made. Just imagine as you stretch that that the thumb or finger is actually getting longer, like rubber, even many feet or yards - like the old cartoon character, "Rubber Man". Otherwise, believe it or not, you can continue stretching for many years, all the while compressing the joints while "stretching" the limb. That's because you have had a habit of "moving and reaching into compression" instead of "moving and reaching into length" and that habit has become very stubborn, and almost totally unconscious.
Part Two: Place and then push your right hand alongside your right leg, in such a way that you compress the thumb more into the mid-line. It is as if you are making the problem worse, bringing the thumb more into the "grip hard" position, that was causing you trouble in the first place. Keeping the hand like that, press the thumb against the leg, but don't let it move very much. This is an isometric that will strengthen the muscles needed to bring the thumb back to normal position. Do this as long as you can until you feel fatigue in the thumb. That won't be long, since these muscles are very weak, and rarely used. Mostly we use their opposing muscles, the gripping muscles. After a few repetitions of doing this, remove the hand and stretch the thumb as before a few times. In time - maybe 6 weeks to 6 months - just like any other muscle strengthening regime, these muscles will get stronger, and your thumb pain should be well gone by that time.
Of course, if you wish, you can create the identical isometric by using one hand to restrain the thumb of the other. Just push the thumb against the resistance. Use whichever is easier for you.
And remember to imagine the thumb getting longer, like Rubber Man could have done, as above.
Do this once or twice a day, and in a week or two your trouble should be gone. I have rarely seen this fail. If then you still have pain in the wrist, or base of the thumb, then please read my article titled Curing and Preventing Carpal Tunnel.