Using a 6-8" piece of 1/2" birch dowel, cope out two sides to narrow to
a flat point the width of your lens threads. Crown the point to a curve
slightly less than the arc of the lens ring with sandpaper or a coping or band saw.
"Resharpen" the tool as it mushrooms out during the straightening process.

Do not use a metal striking tool or try to bend the ring with a pliers.
This will only damage the threads and stretch the metal too far.