First. You should really try looking up this info on the net. There's soo much info on pregnancy out there that there's no excuse for not knowing. You shouldn't be fooling around with anyone until you learn a thing or two about sex and reproduction.
But, to be nice...Here's the thing. If there was so little on your finger that you didn't know if any was there...I wouldn't be worried. Sperm can not survive exposed to air for longer than a few seconds. You both should think about using protection in the future though if you're that afraid of pregnancy. If you had ejaculated and had cum on your finger...Then touched her vagina right after...Then there would be a slight chance of pregnancy. But...In this case, I really can't see how you'd have anything to worry about. Hope this helps!

Unless you had sperm on your finger and inserted it directly into her vagina, there is no way she's going to get pregnant. Relax.

Sperm dies rather quickly when it hits the air be careful.