Well..... personally I'd probably keep the nose screw in and let it heal regardless of whether it was missing the stone or not. Depending on exactly what the jewelry looks like maybe you could sorta color in where the stone should be? I make jewlery, so I'm used to working with really small details. I might end up putting a dot of color in place of the missing gem, but then you have to be REALLY carreful that whatever you used to color it in didn't get in the piercing. Although, I suppose that if you go back to your piercer they could properly change the jewelry out. It's up to you.
