Fertilisation. What should he do?

My cousin had an intimate moment with his girlfriend and he is scared that the girl doesn't get pregnant. the scenario was that the girl had her periods about 3 days ago n my cousin masturbated on the bed not using his hands but by rubbing it over the bed . After ejaculation he touched his underwear slightly from the above and not touching his semen. His finger was not wet or sticky at all and after 10 mins or so he fingered his girlfriend. Before that she touched his girlfriend's body by that index finger of his n after few mins he fingered her.now his girlfriend is worried that she does not get fertile because my cousin touched his innerwear from above be it 15 mins ago n by touching he meant just touching very slightly over the innerwear after 2-3 mins. What should he do ? Pls tell