What is the ruling on one of the worshippers motioning to the muezzin to call the iqamah after the adhan and in the presence of the imam?

There is no harm in worshipers alerting the Imam to the entry of prayer time, as the Companions did during the time of the Prophet, peace and blessings be upon him. This is found in the Hadith of Umar, may Allah be pleased with him: "The prayer, O Messenger of Allah, the women and children have slept," and the Hadith of Usama ibn Zayd, may Allah be pleased with him: "The prayer, O Messenger of Allah." However, the prayer should not be established until the Imam gives permission.