I Have A Swollen Area Just Below The Pantyline On

I have a swollen area just below the pantyline on my upper thigh. (groin?) I injured my leg back in October & have had therapy for a torn minicus. My knee is ok now but I feel like my hip is not working properly. Worse when I get up off the couch. Can hardly walk. There is pain. I first noticed the swelling lastnight, applied ice & it went down but back again today. I was concerned it could be a blood clot due to inactivity after an injury. ( I am a driver) I am 67 years old, have osteoarthritis & degenerative joint disease. If it's my hip what can I do to prevent surgery? Could it be a blood clot? Dimensions are about 2x4".