It is not permissible for a Muslim who has entered ihraam for Hajj or ‘Umrah or both to do anything that may spoil his ihraam, or undermine out his actions. Kissing is haraam for the one who has entered ihraam for Hajj, until he has exited ihraam completely, which is done by stoning Jamarat al-‘Aqabah, shaving the head or cutting the hair, doing Tawaaf al-Ifaadah and doing Sa’ee if one still has to do Sa’ee – because he is still subject to the rulings of ihraam during which intimacy with women is prohibited. But his Hajj is not invalidated because of his kissing his wife and ejaculating after the first stage of exiting ihraam. He has to ask Allaah’s forgiveness and not do such an action again. He can make up for that by sacrificing a sheep which meets the conditions of udhiyah (sacrifice) and distribute it among the poor of the sanctuary of Makkah, and he must hasten to do that as soon as possible.
And Allaah is the Source of Strength. May Allaah send blessings and peace upon our Prophet Muhammad and all his family and companions.