Ok, not trying to alarm you, but I had that happen and it turned out to be a dvt...a blood clot. you may want to go to the er and have it checked. if it is a clot its nothing to play with, but if its not atleast youll have peace of mind.
My mother-in-law had the same thing for 2 1/2 years and no one felt a lump. A physicians asssitant suggested she get an MRI. Guess what. She had a hernia. She just had surgery.
Could be a hernia