Two kids on our team, including my son, have suffered through hip injuries. If it hurts on rotation, I'm willing to bet it's the same one. My son had that injury on each hip at different times. You'll need to have it looked at by someone in sports medicine. Tell them it might be a hip flexor injury. (Chipper Jones had this injury and it really messed him up because he continued to play.) The doctor should be able to isolate it with manipulation and tell if that's the problem. It is most often an injury sustained through an impact like sliding into base or into another player--jarring the hip. According to the sports med and phys therapist, it's not uncommon in younger ball players.
With my son, he had to sit out for 4-6 weeks and do phys therapy until it healed. It just won't get better unless you do and you will play more and more poorly because of the pain. He has learned specific exercises and stretches to avoid this injury in the future.
His teammate, on the other hand, ended up sitting out an entire year. This particular flexor connects to soft bone on the growth plate near the hip joint area. In some cases it can actually rip bone away at that soft spot. This is what happened to his friend, and this is why they will probably do an xray of your leg. Make sure you get it looked at very soon so that a reinjury doesn't create a bigger problem than the one you have.