What is the ruling on the nose touching the ground during prostration?

One of the pillars of prayer is performing prostration. In prayer, after bowing (ruku‘), prostration is made by placing the feet, knees, hands, and forehead on the ground. It is obligatory to perform two prostrations in each unit (rak‘ah) of prayer. During prostration, both the forehead and the nose should be placed on the ground. (Merğînânî, el-Hidâye, 1/51; Ibn Qudamah, al-Mughni, 1/370; Mehmed Zihni, Ni‘met-i Islam, 254-255) For the Messenger of Allah (peace be upon him) would place his forehead and nose on the ground during prostration in prayer, would not press his arms against his sides, and would place his hands at shoulder level. (Tirmidhi, Salat, 201 [270]) Accordingly, if the forehead is placed on the ground but the nose is not, without a valid excuse, it is disliked (makruh). Nevertheless, the prayer is valid. If the forehead is not placed on the ground, the prayer is invalid.

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu