it may be a non-displaced fracture that could be seen on plain x-ray. you can get this at your local physician's office. if the x-ray is normal you can consider it being a hematoma that can take a couple of weeks to resorb.
while playing baseball i was struck just above the knot in my ankle. could there be a hairline fracture? . i'm now at six days with a goose egg on my lower leg and a contusion just under my ankle with discomfort/tightness.