my fingers are bending weirdly, what did I do wrong?

Problem

The bones on the pinky and the ring finger appear to be rolled slightly. This can be caused by excessively rotating or grabbing the bones in those fingers. Because some widgets rely on the local transformations of the bones (especially high-level widgets to control bone-synchronized movements like grabbing, walking, and bending), they can be easily affected by their roll.

To illustrate, I added a generic wolf metarig to an empty scene and generated its rig. The third bone in the tail will be used as an example of how bone rolling affects widgets.

Below is the tail of the metrig, with the third bone in the tail highlighted. No part of the rig was modified.

The generated rig still contains a natural bone structure in a wolf's tail after curling the tail by rotating the end widget.

Now, that third tail bone has been rolled by 190 degrees and highlighted in the next image. Nothing else was modified in the process.

After posing the generated rig, some of the tail widgets are out of tune with the rest of the body, causing the tail to become unnaturally distorted.

Solution

To fix this distortion in your model, I'd compare the roll values of the problematic bones in your metarig to those of the default human metarig. (While it is possible to directly edit the generated rig, I wouldn't suggest doing so because that rig is very complex and contains many hidden bones.) Copying the roll values from the default metarig to your modified metarig should correct the bending motion caused by the rig widget.

Once you are done editing the metarig, tab into object mode and press the "Generate Rig" button in the metarig's Armature settings. This will bring the changes from the metarig into the rig.

For reference, here's a list of each of the metarig's bones in the right ring finger and pinky with their corresponding default roll values:

• hand.R: -127 degrees
• palm.03.R: 148 degrees
• f_ring.01.R: 115 degrees
• f_ring.02.R: 109 degrees
• f_ring.03.R: 95 degrees
• palm.03.R: 144 degrees
• f_pinky.01.R: 113 degrees
• f_pinky.02.R: 109 degrees
• f_pinky.03.R: 101 degrees