Sounds like it could be tendonitis, although you didn't give much of a description. Does it hurt all the time, just when running, flexing the foot etc.?
I would suggest icing it, as well as using some anti-inflammatory cream or sorts. I've had similar symptoms on the outside of my foot. It should go away after a few weeks, and obviously best to rest it.
Foam roll inside and outside calf, and do every calf stretch you can think of a few times a day, as well as icing. It might be from muscle knots in calf, so get it loosened up. After a few days if swelling goes down, I'd roll on the actual tendons with a tennis ball to loosen it up.
Disclaimer, I'm not a physio or anything, but this is what I've done for tendonitis in the past. It might be a stress fracture or something, see what other people say because my advice might be completely unapplicable.
Rest is the main thing though, good luck!