What is the chance that a person get pregnant if the little *semen* come into contact with vaginal lips?

Depends: Depends where you are in your cycle and how far penetration occurred. The labia are outside, while the vagina is inside.

Sex and Fertility: There is absolutely no way to answer your question in regards to your partner's risk specifically. There is just too much unknown here. But, in fact, yes, females who are ovulating can get pregnant with semen deposited near the vaginal opening. It is more difficult and less common than with semen left inside of the vagina, but it is possible.