Hi!
Since there is a knot below the bruise and you have a recent history of fracture surgery, in all probability this is deep vein thrombosis. You will need dopplar ultrasound of the blood vessels of the leg. The other possibility is that the bruise is a result of your fall. Please show this to your doctor. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.