It seems plausible that the rigidity and spasms evident in your thumb may be indicative of arthritis. Arthritis usually leads to soreness, lack of mobility, as well as a burning sensation felt at the joints around such parts as the knuckles and wrists. This could linked with the Tasigna you’re taking. To alleviate the symptoms of this condition, try doing some easy exercises, using hot or cold packs on the area or discussing potential drug changes with your physician.