I'm a teenage girl and i've been having bery sharp pains in my lower nack every now and then, is this worrisome?

It could be: It could be worrisome, if you're having other symptoms like referred or shooting pain down your arm, or tingling or numbness of your arms or hands. Pain in this area can be related to injury or strain and the treatment is Ibuprofen, heating pad & gradual stretching exercises, but if this persists or worsens, you should definitely see a doctor.