There is a tool specially for that - an old guy in a little Swiss valley fixed mine with it in 1982. Looks like something out of a gynecololgists's consulting room.
[thought : maybe Lise has got one LOL]
It is problematic to do tho' and generally not recommended I thought - metal fatigue and all that. The forks have to equally bent out of shape to start with as I recall (like when you ride straight into something and you endo and the bike forks get bent backwards (ie towards the frame))
Might pay to get advice