Hello,
As there was an accident there is always a chance of 
Whiplash Injury. This injury occurs due to sudden thrust to the head and leading to an impression of damage to the 
spinal cord at the cervical region.
 I will advise the first foremost thing to do is taking up an MRI. because that will provide more light to the injury by revealing the internal structures of the 
cervical spine and spinal cord.
Its good that you have not developed any major injury. because in whiplash injury things can go otherwise. Thank god that you are all fine and there is only pain.
Once MRI is done you will be able to notice the extent of soft tissue involved in whiplash injury. Based on the 
soft tissue injury, painkillers along with 
physical therapy will be advised. 
As with physical therapy like 
Ultrasound therapy and TENS therapy the pain will reduce and muscle spasm will be reduced too leading to less pain. 
Any muscles which have gone wasting during the resting phase may need to regain some strength.
Please use the 
cervical collar for time being to avoid more compression of the soft tissue.
Hope I have answered your query. Let me know if I can assist you further.
Take care
Regards,
Jay Indravadan Patel, Physical Therapist or Physiotherapist