Also, rotate your head as much toward the target as you can. The more you rotate your head, the more your nose will be out of the way. Try taking a picture of yourself at full draw from above and behind, so your camera is sort of looking over your shoulder toward the target. Is your forearm in line with the arrow, or is it angled out? Having a forearm that is angled out at release can throw the string into your nose. Make sure you are pulling straight back on the string and not out at an angle that would throw the string into your nose. Try using a glove instead of a tab. The glove should fit snugly with your fingertips all the way to the end.
With a lower poundage bow, it is more difficult to feel yourself pulling through the shot; it is a more subtle feeling. Also, you might be inclined not to pull as much through the shot, because of the feeling that pulling through the shot might make you hit your nose more, but actually it will make it less likely that you will hit your nose.
You are always just a fraction of a millimeter away from hitting your nose under the best of circumstances, and it doesn't take much to throw the string into your nose.
Hopefully, one or more of these things will help. I got a lower poundage bow one time, and exactly the same thing happened to me. But when you figure it out, you will be much more accurate, and it will be worth it.