Should A Five Day Old Painful Bump On Buttocks After A Fall Cause Concern?

Hello, I am a 56 year old female. I recently fell directly on my rear end. I didn't realize I hurt myself until I took a shower the next day. At the time, I just felt a painful lump in my behind. The next day, I looked again and my right butt cheek was beginning to show signs of bruising. The following day I had a TREMENDOUS bruise that is so purple its almost black. I'm going into day five with this bruise and while the purple is beginning to turn lighter, it's becoming more painful. I also think I hit my tail bone pretty hard because its very painful. I'm afraid of an infection. Do you think I should call my doctor and have him look at it?