The artist is obviously not re-using needles. There would be no reason for him to expose himself to the liability of re-used needles, and seeing him open 2 new ones demonstrates that. Even if he did re-use a needle, there wouldn't be anything active on it, considering you were the first appt of the day. Still, it's not really rational to think that he's re-using needles.
The only concern is biotin in an amount >5 mg in a 24-hour period. Your first test, you definitely didn't have that much, and that test was conclusive - ESPECIALLY considering that you did not, realistically, have any risk at all.