Studies of whiplash injuries don't support the use of cervical collars. Many doctors still suggest rest and a collar right after this type of injury. Since it's been a week already you may not need it now. However you should always call your doctor before stopping any advised treatment.
Researchers report better neck motion and more pain relief after a whiplash injury with early physical therapy using joint mobilization. Joint mobilization is a way the therapist can move each neck joint through part or all of its normal motion.
There is much we still don't know about how to treat whiplash injuries. Physical therapists are actively studying this problem. Researchers are comparing different treatments for neck pain after whiplash from drugs to the use of ice packs to exercise and physical therapy.