Many people use tied-on nocks when shooting 3 under for that reason. Other than that, try rotating your head so it faces the target more and your nose is more out of the path of the string. Make sure you bring the bow to your head and don't tilt your head into the bow when you shoot. Make sure you keep your head absolutely still from release through follow-through. This is tricky. I was sure I was keeping my head still, but it was moving. I had to increase my awareness level of when it was still and when it was moving to a higher degree to solve this.