As stated by the other physician in this forum you have pretty classic morphed-en coup de sabre. It is an autoimmune condition that is a localized variant of scleroderma. You should have an evaluation by a dermatologist with an interest in connective tissue diseases and autoimmune conditions.
What you have is an enlarged wrist vein. These veins can enlarge when hand and forearm activity is increased because more blood is flowing through them. Exercise and rapid hand movements can increase the blood flow. I do not think that you should have any fear of this bleeding, but...
Thank you for your question.The vein is quite sizeable and perhaps you would have been best served with a microphlebectomy technique. Having said that, hyperpigmentation does occur with improper compression after the procedure and not following with a regimen of wearing compression stockings ...