My son has little purple dots from neck to toe and is sensitive to touch on neck and chest what could it be and should i take him to the er ?

Consider Petechia: "purple dots" can represent rash known as petechia. If you push on the rash, and it does not blanch - consider either petechia or purpura. While petechia are usually associated with self-limited viral infection in kids, can be present in more severe infection like sepsis and bacterial meningitis. Should be evaluated asap, especially if associated with fever and/or neck pain.