My 19 year old son has a headache and sudden onset of neck pain. Woke this morning w/ mild neck pain increasing throughout the day. Need 2 worrry?

Maybe. I would take him to his pediatrician or primary care doctor. Is he in college? Sometimes this is the first presentation of meningitis, which can be serious. Usually this progresses rapidly to cause fever, headaches, and neck stiffness and pain. It can be bacterial or viral.
See Dr ASAP. Can't say for sure what is going on but if this is the first time for such symptoms, you need to see a dr. Asap!