Hate to tell you this but I'd have preferred a diagnosis of stress fracture: six weeks rest and it's done, probably. Ruptured ligament, depending which one, could take a LOT longer. Good luck for healing.
Stress fracture/fracture does seem likely - get it checked out. (If the doc prods the foot from underneath and you hit the roof, yup, you've probably got a fracture even if it doesn't show on x-ray. (N.B. about 50% of stress fractures don't show up on x-ray).