Get cleaner coke or clean it yourself. Unfortunately it's from the cut and there is nothing you can do about it. I had a friend of mine buy a kilo (yes saw it with my own two eyes) and he said the dealer used a tester in front of him shown to be 92-96% clean coke and I did an 8ball over the course of a good chunk of a single day, woke up in the morning and my nose was perfectly fine as if I had never done even a single line.
Familiarize yourself with "Cocaine Acetone Wash" and clean your coke up. It's not worth it for only a gram or two, but a quarter would be well worthwhile.
Also keep in mind cocaine in and of itself isn't quite as "Speedy" as the cut cocaine is. There is a burst of energy, but some people get coke that is cut and say they have an incredible amount of "Speed" that comes over them. It's from most likely the ephedrine or other cuts used. Just clean your coke yourself, you'll be much happier with the product.