You sacrifice it.
Sahih Muslim Book 35, Hadith 21
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Allah's Messenger (ﷺ) led us in the 'Id prayer in Medina on the Day of Sacrifice. Some persons slaughtered their animals ahead of him under the impression that Allah's Apostle (ﷺ) had-already offered sacrifice. Thereupon Allah's Apostle (ﷺ) said: Those who had slaughtered their animals ahead of him should slaughter the other ones in their stead. And they should not sacrifice the animal before Allah's Messenger (ﷺ) had sacrificed (his animal)
Sahih Muslim Book 35, Hadith 20 Next Hadith → Allah's Messenger (ﷺ) distributed sacrificial animals (amongst us for sacrificing them on 'Id al-Adha). So we sacrificed them. There fell to my lot a lamb of less than one year I said: Allah's Messenger, there has fallen to my lot a lamb (Jadha'a), whereupon he said: Sacrifice that.
Sahih Muslim Book 35, Hadith 22
Sahih Muslim Book 35, Hadith 20 Next Hadith → Allah's Messenger (ﷺ) distributed sacrificial animals (amongst us for sacrificing them on 'Id al-Adha). So we sacrificed them. There fell to my lot a lamb of less than one year I said: Allah's Messenger, there has fallen to my lot a lamb (Jadha'a), whereupon he said: Sacrifice that.
Sahih Muslim Book 35, Hadith 22