Reference: Fataawa al-Hajj wal-‘Umrah waz-Ziyaarah – Page 64
Question: I performed the obligatory Hajj and one night, while I was in Minaa, I had a wet dream and was unable to make the ghusl. So, is there anything required of me?
Response: Having a wet dream whilst in the state of ihraam for the Hajj or the ‘Umrah does not affect the Hajj nor the ‘Umrah, so they are not invalidated. Whoever experiences this should make the ghusl for the janaabah after waking up from the sleep, if he saw semen, and there is no expiation upon him because having the wet dream was not out of choice.
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet ﷺ and his family and his companions.