In 40 years of history, there has never been a single case of infection from a external surface. A scratch is not a cut open enough to lead to a infection. In order to get an infection through a cut, this one should be HUGE. You wouldn't be exposing such a big cut to the environment as it would be too painful.
By the way, out of the body, the air damages the surface of the virus and it's unable to infect, even in seconds.
The only ways HIV is transmitted are :
-Unprotected anal/vaginal penetrations.
-Sharing needles to inject drugs.
-Mother to child.
All the best.
Semen outside the body?? Test is not needed for your scenario