Whats Wrong With My Leg ?

Well, today in P.E we were playing Badminton and i tripped over my trainers, but sideways, if i make sense lol and now the area near my ankle but on the outer side is really paining me. my little sister maged it for me which was nice of her but i dont know whats wrong with my leg. my mum says theres nothing wrong but the pain is excruciatiing :| i can walk but its like im limping. my leg feels fine except for the pain ... is there anything wrong ?