Any neck injury, such as whiplash should be fully evaluated by a health care provider.
In general, injuries involving soft tissues, are similar to a cut on your finger. When a tissue, such as a muscle, is involved in a neck injury, it tears and bleeds. When the bleeding stops a scab is formed. After the scab falls off a scar is left. Scar tissue is weaker, less elastic and more pain sensitive than normal tissue.
During the initial tear of a muscle in a neck injury, there is inflammation present often for the first few days, so it is important not to use heat for neck pain relief which would cause more inflammation. Cold applications are appropriate until any swelling and inflammation is gone along with a soft type of neck brace to help limit further tearing and prevent sudden temperature changes.
It is important to remember that muscles will start to weaken just a few days after motion is restricted. It is important to minmize inflammation so that motion can be restored thus minimizing scar tissue formation and muscle imbalance to limit chronic neck pain.