Here are the only risks for transmitting HIV which include having unprotected vaginal or anal sex or sharing IV drug needles to inject with. These are the only risks. Air inactivates the virus. This is why something can 't touch you, even CUT you and transmit the virus. Even if the blood appears fresh. JessyJames is very right that this is ZERO risk. No one has ever gotten HIV this way in the history of HIV! And there is a long history of research with HIV at this point. People do not get HIV from an object that cuts them.
If we assume the sharp object (say a piece of glass from broken beer bottles at this pub), was contained with body fluid like blood and this blood was once HIV infected, then you chances of getting infected is zero.
So there is no chance of getting infection from HIV in this way.