You are likely to have a bony contusion either in isolation or along with muscle contusion. There are a few muscles/tendons which run medially (on the inside of your ankle). Namely Flexor Digitorum, flexor hallucis longus and the tibialis anterior. You could have also suffered a contusion to the medial aspect of the achilles tendon.

Rest, ice, gentle massage. Use of a compression bandage. Stretching in particular for the achilles tendon will help. Seek some treatment just to be sure you haven't done any more serious damage.

Hope this helps