My Sister, Age 53, Has Been Complaining Of A Nerve/vein

My sister, age 53, has been complaining of a nerve/vein on her hand running from thumb to upper arm, which is now swollen, and continues to be so for days now. Any movements of the thumb, including trying to lift something heavy is very painful. Met with a general practitioner who suggested surgery as an option. I would like to know what is her condition, and why drugs can't be used to treat her condition?