Skin reaction before an important event! Help?

I was trying a new cream few days before and I got some sort of nettle-rash - not color changes, though, but the skin is not smooth at all, it itches and even a few pimples appeared! AND I can't wear any make-up there to hide it. It's in 3 days and my skin condition is horrible! What can I do to improve it quickly? Olive oil never failed me before. Would it help now? Or what would?