A few weeks ago I engaged in BDSM play with two friends who I didn't know well. No sex was involved, but at one point there was a spiky paddle. It was used on me and only after did I realize that droplets of blood were forming. A few hours earlier it had been used the other member whose HIV status I'm not SURE about (though she seemed like she'd have mentioned it). I also know one member of the couple had a history of drug use. How significant is the chance that I acquired HIV (or anything else?) from this encounter, and should I plan on getting tested based on this encounter?