[jonny1986]

last day i had my back pack open and my 645d plus 35 fall down at home from 1,7 meter!! incredibly the body suffered not even a scratch, probably the lens it the soil before diminishing the impact of the body, the lens suffered a bump to the filter ring. it's all metal and that spot is not curved inside and i cannot mount any filter. do you know a way to straighten it?

[kharry2012]

Don't use anything metal--will just bung up the threads. Instead use a wooden dowel and a mallet. If you cannot find the right size dowell at your hardware store, you can just make your own.

[desertglow]

you need something like this:
Lens Filter Ring Vise