Suggest Treatment For Left Buttock And Back Pain After An Accident

Hi, I was in a minor car accident over a week. I have bruising near the top of the left side of my bottom. During the week the pain was quite spread down my back etc but as that has disappeared im able to pinpoint pain in one area towards the left cheek where the brusing is. It is not sore to touch from the outside but I get stabbing pains when sitting in certain positions or bending over to get something off the floor. My left hip is starting to hurt too. I went yo a doctor straight after the accident who said it was just tissue damage but didn t take X-rays but felt around and pushed on a few places but I feel that it may be something else considering the other muscler pain has gotten better but this stabbing pain is still there! Could you please give me an indication as if I should leave it or head back to another doctor?