What Is The Treatment For Sharp Pain In The Arm?

I have sharp pains and throbbing in my left side and arm. It's worse at night when I lie in bed. I have a history of bad backs in my family, but I doubt I should be having this pain so early in. I'm only 14 years old and I don't know what to do. I've already gotten an EKG and they said everything is normal. I'm just confused about what I have...