HIV is unable to reproduce outside its living host (unlike many bacteria or fungi, which may do so under suitable conditions), except under laboratory conditions; therefore, it does not spread or maintain infectiousness outside its host.
HIV is transmitted by;
Unprotected penetrative anal and/or vaginal sex
Sharing works with other IV drug users
Mother to child
HIV cannot survive outside the body. It inactivates when exposed to the environment rendering it unable to infect.
but i am afraid that there was some bodyliquid on his finger.
No risk. You cannot get HIV from the scenario you describe.