Buckle Mark in Print
Doesn't look like it would be that hard to carefully burn in that streak just a bit to match the sky.
Depending on how many copies you want after you have made your correction you can rephotograph the print and use that to make the extra copies to make it easier on yourself.
You can also add in clouds if you choose to make a composite of the scene with a mask to cover that area.
Also are you using a glass neg carrier? A tight one sandwiching the negative may reduce the appearance of that bend.