Our employee (EE) was in boom lift going from conveyor 1702-1902. Lift operator's hand slipped off joystick, then oper grabbed it again roughly. The jerk in movement of lift caused our EE's head to thrust back & then forward quickly. Our EE felt a twinge in neck, but EE didn't think much about it. On 02/15/2023, the pain had become bad enough that our EE sought medical treatment.