What Causes Pain And Bulging In Veins Of Hand?

Recently the veins on the back of my hands have become bulging and painful clear up into my wrist. It is more pronounced in my left hand. This usually happens later in the day and not every day. Lifting my hands above my head relieves the symptoms immediately, but I cannot get my work done with my hands in that position. I have been monitering my blood pressure lately, because it has been spiking high for no apparent reason. I have been riding my bike daily for 1/2 hour for the last two weeks to help lower my blood pressure. The hurting veins have been more noticable during the last two weeks, but I also had a problem with them for a short while earlier this past summer. I do not smoke. I am not overweight, but do have high cholrestorol for which I am taking red yeast rice. Do you have any advice? Thanks.