Do you have to go to the doctor for a broken tailbone? i hit my lower back when a ocean wave hit and hit my back on the bottom. its sore but bearable ?

Your choice. On the one hand you can confirm or exclude your self diagnosis. On the other, there is seldom they would do anything other than treat discomfort with pain meds and send you home. If/when it bothers you enough go in.

If it is "sore but bearable", sounds like bruising, not a fracture. Likely, if this is the case, give it a few weeks and it should stabilize. Sitting may exacerbate symptoms, so a "donut cushion" might ease the way until stabilization.. If symptoms worsen, contact your physician.