Just keep using it an eventually it will become stronger and easier to use. In just the 3 weeks since I picked up the guitar again my pinky has become much easier to use.

When I first took lessons many years ago, I never used the pinky because it was too hard, caused it to ache and didn't want to cooperate, but since I have been here on this site I don't have the same trouble.

One of the instructors here, probably all of them suggest using the pinky even if it easier not too, the only way to get good at it is to use it, and keep at it.

Hope this helps
Jaime