It is quite relieving to know that you have not suffered any kind of damage to the spinal cord. Spinal cord damage can leave you paralyzed, but if the doctor says that everything in the area appears fine then you are probably just experiencing some muscular damage.
Muscular damage to the back and neck are very common injuries that your body would be subject to in a lifetime and are not dangerous or life threatening in anyway. However the muscles require that you give the injured area sufficient rest while the injury heals. After the healing, you need to reacquaint the affected muscle with regular movement again and slowly get it used to regular use; otherwise, you could end up injuring the muscle all over again. Some of the common injuries to the muscles connected to the back and spine are repetitive stress disorder, stiff neck, whiplash, and a host of other conditions. The treatment of your injury specifically would need you to take a week of rest at the most. Since the injury you sustained is in your tailbone and your X-rays are clear, the first thing you need to do is to find a posture where there is absolutely no pain. The possible postures could be when sitting upright, lying down face up, lying face down, sideways, or any position that does not place weight on your back. It is important to note that any act of carrying an object would place an abnormal amount of weight on your spine. The human spine acts as a focus of a lever and the weight of an object and the force exerted to lift the object are both borne by the back. Therefore, any kind of activity that requires that you exert your back should be avoided.
One of the more common repetitive injuries that occur is when not rising from a resting position in the correct manner. Most healthy people do not really give too much importance to rising out of a resting position and end up literally jumping out of bed. You would have realized by now that this has to be done with a certain amount of care. When you do have to get up from a resting position, do it slowly; one leg at a time; using the arms to lift the body and not the back; and transferring more weight to the legs than the muscles of the back.