Can I still say Kiddush Lavana?
Kiddush Levanah can be said until the fifteenth day of the Jewish month.
According to the Rema, kiddush levanah can only be recited until midway through the month (meaning, even on the fifteenth night one cannot say kiddush levanah through the night, but only until the midpoint of the month, the calculation depending on the precise molad of the current month and the next month).
Therefore, kiddush levanah cannot be said tonight (the sixteenth of Av).
See Shulchan Aruch 426:3, Taz, and Mishnah Berurah 17-19.