Is there a risk from dry pre-ejaculate?
If I had somehow (which I don't think I did) got pre-cum on my fingers, and then immediately wiped it off, and it was completely dry, and I then poked my girlfriend a few hours later, what would be the chances of pregnancy?
Sperm are hearty, but they're not that hearty! As long as your hands were dry when you had contact with your girlfriend, you've got nothing to worry about from this situation. Dry ejaculate or pre-ejaculate poses no risk.
I'm not quite sure what you mean by saying you "poked" your girlfriend, but I'm going to assume that you mean that you preformed manual sex on her. (Of course, if you poked her in the arm or leg, there's no risk of any sort from that anyway.) However, I will note that if you preformed manual sex on your partner without at least washing your hands immediately prior to the contact (or preferably using a glove), you could have put her at risk for developing an infection. Hands are notorious for carrying germs, bacteria, and other nasties that can easily be introduced into her body through unprotected manual sex and can cause infections. So in the future, it would be best to make sure you at least wash your hands (and that your hands and fingers are well groomed and smooth so that you don't cause tears or abrasions) beforehand.