All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If you delay the Takbir (saying “Allahu Akbar”) upon rising from Sujud (prostration) until you are fully standing, then its prescribed time has passed, and you are not obligated to say it afterward. Your prayer remains valid according to the majority of scholars, who consider the Takbir for transitions between postures a recommended Sunnah.
Saying the Takbir after standing incurs no sin. At most, it could be considered mentioning Allah’s remembrance where it is not prescribed. However, this deliberate addition does not invalidate the prayer.
Sujud As-Sahw (prostration of forgetfulness) is not required for adding this Takbir, even if it is done intentionally.
Allah knows best.