You can try this, it has worked for me.
If it is a very small twist, just twist it back the other, lightly, way until it is straight. But be careful not to put a lot of pressure during the twist, you can break the limb.
If that does not work, use a blow dryer or hot water to heat the limb in the area of the twist. Get the limb warm on both sides, not so hot it hurts the hand if you touch the hot limb. Then twist it lightly in the opposite direction of the twist. When it is straight, pur it under cold water to cool it quickly.