What Causes Burning Sensation In Wrist?

hey, about 2 days ago my left wrist started hurting. On the top of my wrist I have a vein that goes down through my hand , past the top of my wrist and into my arm. when i look at it it looks swollen and it pops out where the top of my wrist is and now its the 3rd day and i cant take the pain anymore. what is wrong with my swollen vein wrist?