What should one do if they forget to recite Du’a al-Qunut in prayer?
If a person praying forgot to recite Du’a al-Qunut and thereafter proceeded to the Ruku’, if he remembers after this then he should not come back into Qiyam, rather he should perform Sajda al-Sahw at the end of the prayer. If a person in such a scenario returns back to the standing position, but does not perform the Ruku’ again, the Salah will be invalid.
And Allah ﷻ knows the best
Imam Ahmad Rida Khan رحمة الله تعالى عليه
Translation by Dr Musharraf Hussain Al-Azhari Translator of Majestic Quran, www.majesticquran.co.uk