Hi

i'm an 18 year-old male and in great fitness (run track, x-country). A couple of days go I stood up from a sitting position I was in for maybe 5 mins. I started to walk and felt a sharp pain ontop and slightly inside of the iliac crest (right side of body). It is not in front; it is more to the back or side. This pain only occures when I place weight on my right foot (while walking usually). It is not extremely intense, but the duration is short and mildly painful. I've had this pain now for two days and no intense physical activity that I know of could have caused this pain (i am taking weeks off from running). Please give me an idea of what this could be.