Praise be to Allaah.

If the tawaaf that you are asking about was tawaaf al-ifaadah, which is the one that is done after standing in ‘Arafah, then your tawaaf is not valid and this Hajj is not valid, unless you repeated this tawaaf, because tawaaf al-ifaadah is one of the pillars or essential parts of the Hajj. So you have to go back to the Sacred Mosque and circumambulate the Ka’bah seven times, starting each circuit from the Black Stone and ending the seventh circuit at the Black Stone, and each circuit must go outside Hijr Ismaa’eel from behind the wall. Thus your Hajj will become acceptable. But if the tawaaf in question was the farewell tawaaf, then you have to offer a sacrifice to be slaughtered in Makkah and given to the poor, in order to complete your Hajj, but you do not have to go back to the Ka’bah, and if you do go back it will not waive the obligation to offer a sacrifice. But if it was a naafil tawaaf, then you do not have to do anything. 

And Allaah is the Source of strength. May Allaah send blessings and peace upon our Prophet Muhammad and his family and companions. End quote. 

Standing Committee for Academic Research and Issuing Fatwas 

Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz, Shaykh ‘Abd al-Razzaaq ‘Afeefi, Shaykh ‘Abd-Allaah ibn Ghadyaan, Shaykh ‘Abd-Allaah ibn Qa’ood. 

Fataawa al-Lajnah al-Daa’imah li’l-Buhooth al-‘Ilmiyyah wa’l-Ifta (11/234).