Welcome to HCM
You mentioned in your query that you are an active senior and have been exercising regularly. Swollen ankles could suggest at your age could suggest arthritis
. Your right leg could have had cellulitis
which is caused by streptococci bacteria. This infection affects skin and subcutaneous tissue
which spreads very quickly and should be controlled by intravenous antibiotics. I suspect the infection has spread to your ankle. I would suggest you visit a orthopedic doctor and undergo synovial fluid
analysis to rule out any infective cause of arthritis. I would also advice you to take rest until the pain has reduced and do not over exert yourself.