Tucking the pinky of your bowling hand to the first knuckle can cause the ball to hook a little more. When you first try this, it might feel as if you’re going to drop the ball. Keep after it. You’ll learn to do it and find that it gives you an alternative ball reaction. You might want to wear an adhesive bandage across that knuckle for a while as a callous might develop. Keep in mind this is an adjustment. If your ball is hooking too much or too soon, untuck! You also might want to untuck it on your spare shots.
One caution here about tucking the pinky. With some people, tucking the pinky can put strain on the ring finger. If you try this and notice your ring finger beginning to hurt, either have your pro shop professional shorten the ring finger span very slightly (for instance, by 16ths until the pain stops) or stop tucking. The added hook potential is not worth an injury.