Your metal is stretched and oil-canning. You need to find a way to shrink it, first find the high spot of the damaged area, warm it up with a set of torches, so it is cherry red (not a big area though,smaller than the size of a dime), with someone on the inside holding a dolly on the hot-spot, strike it with a firm but not forceful blow, just once. Then while it is still warm tap gently around the hot-spot moving the metal into the center of the hot-spot. Quench it with compressed air, or a damp cloth.
Keep in mind the 2 basics of metal work,
Hammer on dolly stretches the steel
Hammer off dolly shrinks the steel.
Hope any of this helps in your quest for a straight nose