What Causes Brown Rashes On Skin, Chest Pain And Headache?

My son has develop a rash like light brown and it times it looks purple straks know hw has being having chest pain and bad head aches can all this be related His Dr saw him back in Dec he said if it did not go away in 6 months he will sent him to a demartalogist to get some testing done should I wait or ask Dr that I want this done sooner