On the afternoon of Tisha B’Av, Nacheim is recited in the middle of V’Lirushaliyim in Shemone Esray. If it is forgotten, it should be recited in Retzei before V’Sechazenu, but the concluding bracha of Nacheim should not be said. If it is recited in Shema Kolenu, it is aceptable after the fact. If it is not stated in Retzei, the individual should finish Shemone Esray and not go back to recite it.