I started having pain on right side of neck all of a sudden. Pain has worsened & is now hurting all on right side of head to shoulder. It's been3days?
It might be a muscle spasm which could transfer from the neck to the shoulder. This could be triggered by injuries, abnormal movements, or also if you have been recently sick the muscles can be sore after the illness.
Treatment with warm and cold packs and anti inflammatory medication can help with symptoms.