I'm sorry, you can't cure it instantaneously. The oils have damaged your skin, and it will take at least a few days to heal.
You can however use tea tree oil rubbed into the rash as a way to stop the itching and speed healing. Or you can use 50/50 tea tree oil and lavendar essential oil. When the rash begins to heal and gets very dry, you can continue the oils or use aloe vera (you can find the leaves in many grocers. Slice it open and use the gel inside directly).
Before bed you can use an oatmeal bath. Several cups of oatmeal with some baking soda added in. Soak for 30min. You can grind regular oats into a powder with a coffee mill or grinder or just buy the ones pre ground for baths.
The zinc in calamine lotion can also help, but won't speed healing like tea tree oil.