I caught a heavy binder & it bent my wrist backwards. The cyst arose from that trauma. Diagnosis was sprained wrist & tendonitis but it's been 10 mos.?

X-rays can help rule. Out a more severe injury or a ligament injry that needs attention. If a cyst formed it may not just go away by itself as well. If xray is negative and a ligament injury or fracture is still suspected then at times more advanced imaging is used such as mri.
Wrist Pain. May represent a wrist ligament injury, ganglion cyst, or tendon insertion injury by your description. If not improved after 10 months i would have evaluated by musculoskeletal or hand specialist.