i am an athletic trainer; sounds like you could have a strain (tear) to your plantaris muscle. the plantaris is a small muscle (that really doesn't do a lot) in the calf area. Yet, if it is irritated- either strained or torn it can be a significant problem that in my experience takes weeks -even months to resolve (during this time you will have to avoid activities that irritate this injury otherwise it will not heal). Normally rest- ice or heat- and- after 1-2 week- some mild stretching can be initiated- then gradually increased the stretching program -and- finally, you must continued with the stretching program after you return to activity otherwise it is very susceptable to re-injury; however, i recommend that you see an orthapaedic physician first, in order to confirm it is the plantaris- and, advise you. best of luck-mm- ps. my experience is that many athletes with well developed calf muscles develop this condition because the larger muscles of the gastroc (calf) over-stretch the plantaris during exercise or sports.