Could be. If it is, running on it, especially at that weight, is not a good idea. A high ankle sprain involving ligament or multiple ligament damage may take months to heal, and could require some immobilization, screws, or surgery. The only way to know for sure is to have it professionally diagnosed, which can easily be done by squeezing and twisting the ankle at that location. It depends on the extent of the sprain, if any. It is an outward twisting injury that would not be common in runners, at least due to running.
Do you have a history with this injury, or have you played other sports that involved twisting or pivoting on the leg? This injury has claimed many a high profile professional athlete, but I'm not sure how you would get it doing C25K. Were you running on uneven ground? Maybe there could be a tie-in if you were an excessive pronator, combined with lots of repetitive motion you are not physically prepared for.
A good diagnosis would probably rule out stress or avulsion fractures, so it may not come cheap after scans are done and read. In the meantime, feel the adjoining areas with your own fingers to get a better idea of where the pain is actually coming from. There is some possibility of muscular strain, more likely when it "warms up" good, but there would probably be other symptoms in the leg or foot.
For example, damage to the inner heel could cause the Abductor Hallucis muscle that lines it to shoot pain from the heel upwards above the inner ankle. Excessive pronation could produce this problem. Have you ever had a gait analysis done or other biomechanical evaluation?
Flexor Digitorum Longus that lines the rear inner calf could also produce pain there, but would probably be felt mostly in the bottom of the forefoot where it attaches to flex the toes. Squeezing the calf down there applies pressure to the muscles at that location, in addition to testing the ligaments that hold your leg bones together, for damage. Muscles should not hurt when squeezed, but when injured, can hurt with varying intensity from dull to sharp, usually somewhere in the middle. Torn ligaments would probably be more painful when subjected to the twisting motion that strains them. The distinction needs to be made. Soon.
The sharpness of this pain is what bothers me enough to advise you to get a diagnosis before spending any more time beating the streets.
ANKLE JOINT PAIN Observe how the cuboid on your studying left (actually the right foot) in this CT check out has been seriously subluxated. This woman hasn’t been able to put her high heel on the floor for 11 decades. And she is only 36 decades of age. While any one of the tarsal cuboid can be harmed, I find in exercise that the cuboid cuboid is often the key to many ankle accidents.
Just like any other combined, if a concentrated joint is not decreased, it will lead inexorably to Immobilisation Osteoarthritis. Within these so-called synovial joint parts there is liquid putting about holding important nutritional value to the hyaline fibrous that collections the cuboid. You can see the arthritis very clearly in the CT above in the talo-navicular combined. That’s what happens to concentrated joint parts that are not decreased. IMMOBILISATION ARTHRITIS …