Suggest Treatment For Seroma In The Groin Area

Hello, I have a seroma in the right groin area about size of a small walnut. I had an ultrasound and showed a seroma, although I have not had any surgery, and don't know if I have had an injury or anything. It has been there about 6 mo. Not sure if I should be concerned, my Dr. said wait a couple more months to see if it lessens. I am slender, so it shows up more on me I guess. Do I need to be worried that it is something more serious? Thanks , Tonyia