There is some internal damage or the tree wouldn't still be bent. But the damage isn't too severe or you would see something on the outside: vertical splits or horizontal wrinkles in the bark. I think your best hope is to tie a rope that is padded (so it doesn't further damage the trunk) around it above the bend and pull it straight. Then you can secure the other end the rope to the ground or another tree. If possible, give it a splint against the trunk to keep it from moving too much. Eventually the tree will re-grow the damaged cells in the trunk and it will stand straight by itself.
Its a pretty tree with 30 years of effort into it. Don't give up.
Daisy
