Hi! I just noticed that suddenly when I have my right arm by my side, the veins on the top of my hand become very prominent and bulge slightly. There is a slight stinging sensation on the top of my hand when this was happening. When I raise my arm up above my head, or raise my hand into an upright position, the veins return to normal and disappear, until I put my arm back down again. This is not happening on the left arm or hand, just the right. What could cause this?