You should go see your doctor, as you may have what is called a Ganglion Cyst. Ganglia are thin walled cysts filled with clear fluid arising from joints or tendon sheaths. They grow on the top of the wrist (dorsal ganglions), underside of the wrist, at the joint of a finger and occasionally affect the feet.
There is non-surgical treatment to massage surrounding tissue or remove (aspirate) the fluid contained in the cyst. There is also surgical treatment, should the cyst reappear. A section of the tissue that lines the joint or tendon is removed along with the cyst. This helps to keep another cyst from forming.



