What Causes Sharp Pain In The Left Hand ?

What could be causing me pain. I have a sharp pain in my left hand when bending my hand back, all of the pain is around the back of my left hand near my wrist but not on my wrist. As to like push myself up from a sitting position or just doing anything any lifting. This pain is very sharp and weakens my left hand, I have also noticed my left hand when doing what I just mentioned the veins in my hand protrude outward more (more visible) then normal. So what could be the problem? This has been going on for two weeks? There are no visible abnormalities on my left hand, bumps or etc.