Most do not feel serious pain during the first few days following an auto accident.  Most will have headaches, sleeping  problems, trouble concentrating, or dizziness at first.  The pain  usually increases over the next 3-10 days, stiffness and muscle spasms  get worse, and usual activities become difficult or impossible to  perform.  The bones in the spine get pulled out of alignment, spinal  discs may be torn, ligaments may be lax, any of which could be a  permanent injury, and could cause pain, tingling or numbness that may  never go away.  It is very important to get checked for these injuries,  and if they exist, to begin therapy right away to try to get you back to  normal as soon as possible.