I scratched my eye and it really hurts, what should I do?  

Go to a doctor. Visit an eye doctor as soon as possible. Refrain from putting any drops in your eye until you consult a physician as some eye drops can exacerbate the condition.
Get evaluated. You have a corneal abrasion. This is a traumatic loss of the skin covering the cornea. This is, as you have discovered, very painful and may disturb the vision. You want to make sure that there is no eye penetration. Best to see an ophthalmologist who can make sure there is no other problem and recommend treatment.