Q: Does the person who forgetfully goes past the Miqat (site for entering the ritual state for Hajj and `Umrah) have to return to it? Is there anything required of him?

A: They are required to return to it, if they have not yet entered into the state of Ihram (ritual state for Hajj and `Umrah). If they have already entered into the state of Ihram, they will not have to return to it but will be required to offer Dam (sacrificial animal offered in atonement required of a pilgrim for a willful violation of a prohibition or obligation while in the ritual state for Hajj and `Umrah).

[Fataawa Shaykh Ibn Baaz - Alifta.net]

See Also:

The ruling on passing the Miqat more than once without assuming Ihram

The ruling on one who goes past the Miqat without intending Ihram