Praise be to Allah.
Shaykh ‘Abd al-‘Aziz ibn Baz (may Allah have mercy on him) said:
“Whoever wants to offer a sacrifice should not remove anything from his hair, nails or skin once Dhul Hijjah begins, until after he has offered his sacrifice because the Prophet (peace and blessings of Allah be upon him) forbade that.
Umm Salamah narrated that the Prophet (peace and blessings of Allah be upon him) said: “When the first ten days (of Dhul Hijjah) have begun, if any one of you wants to offer a sacrifice, he should not touch (i.e., remove anything from) his hair or skin.” (Narrated by Muslim)
But whoever removes something from his hair, nails or skin during the first ten days of Dhul Hijjah out of forgetfulness or ignorance of the ruling, when he has resolved to offer a sacrifice , does not have to do anything. Allah has forgiven His slaves for mistakes and forgetfulness in this and similar matters. But whoever does that deliberately has to repent to Allah, but he does not have to do anything (i.e., he does not have to offer a fidyah or kafarah (expiation).”
And Allah knows best.