Dean, just to add a bit more to boxing coaches suggestions.

Early natural movement's good - watch out for over inwards rotation when you flex your little finger. Buy climber's putty to strengthen grip. Work your index, ring and little fingers together (3 finger grip - without your pointing finger).
Test your little finger's strength by comparing with the other one - keeping them straight press down on the nail. You'll probably find that the injured one can't stay straight and feels weaker. Get a small pliable elastic band and link up the thumb and little finger then straighten to full extension (opposite of a grip).

Let me know how you get on.