I've been hit repetitively on my inner right ankle. I now how a hard mass that's been there for almost a year. What could it be?

Ankle knot. Repetitive striking of a bone, in this cases the inner ankle (tibia or medial malleolus), can cause bony changes. Reactive changes such as hypertrophy of the bone, or a bony growth can develop as a result of the constant trauma to the bone. Try and wear a shield like in soccer to avoid hitting the inside of the ankle.
Swollen. It can either be a bone bruise or a hematoma.