When a nerve is irritated or it's supply of nutrients disrupted, it can become overly sensitive.  The muscles attached to it can become tight and filled with trigger points.  This phenomenon occurs because the receptors in the nerve and muscle get deprived of their chemical signals and start to make themselves more sensitive to any signal.  A good example is walking out into broad day light after being in a movie theater.  While in the movie theater, the receptors in the eyes become overly sensitive to light in an attempt to adjust to the new environment.  However, when they get bombarded with the light of day, they get overloaded, causing their owner to sense pain and confusion (a "white out").  The muscles and nerves react in the same way.  When a nerve is compressed or irritated in the neck, the skin innervated by that area and the muscles attached to that nerve can become hyper-sensitive to any stimulus.

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