He forgot Sa’ee’
Question

I did my obligatory Hajj, and I did it as Tamattu’, so I did ‘Umrah then I exited ihraam. On the eighth day (of Dhu’l-Hijjah) I entered ihraam and did all the pillars of Hajj, but I inadvertently forget Sa’ee. What do I have to do? 
Please advise me, may Allaah reward you with good. Is my Hajj valid or not?
Praise be to Allah.You have to go back to Makkah and do Sa’ee for Hajj, because the one who does tamattu’ must do two Sa’ees, one for ‘Umrah and one for Hajj. 
And Allaah is the Source of strength. May Allaah send blessings and peace upon our Prophet Muhammad.