Have any herbicides been applied near your sunflower? Some types of herbicides can drift from surrounding areas and cause sudden unusual symptoms like curling, distortion, or discoloration. Do you see any unusual symptoms on other plants nearby? Refer to our webpage for more information on herbicide damage. https://extension.umd.edu/hgic/topics/herbicide-damage
This is a good resource as well: https://www.extension.purdue.edu/extmedia/id/id_184_w.pdf
All you can do is wait and see if the plant is able to grow out of the symptoms. It is not too late to re-plant sunflowers.