What COULD be wrong?
If an arrow was shot through the back of the head, it would go through the skin/ scalp, muscle, blood vessels, nerves, bone ( skull or neck vertebrae ), the outside lining of the brain or spinal cord, the brain or spinal cord.
Many kinds of disorders with any of these structures could cause a pressure feeling.
See ur doctor if symptoms persist.A stiff neck
can be urgent and require immedeate attention.