Per Sunnah one should not eat before Eid prayer and should eat from their qurbani on Eid ul Adha.
What needs to be done on 2nd or 3rd day when one just offered the Eid prayer on 1st day but is performing the qurbani on 2nd or 3rd day?
الجواب وباللہ التوفیق
It’s only Preferred not to eat before Salat ul Eid on Eid ul Adha, if there is any excuse then there is no harm in eating, and even after Salat ul Eid to begin eating with the Qurbani meat is also Preferred only, it’s not Fard or Wajib. Therefore, if one feels hungry or there is delay in doing the Qurbani then still there is no sin or harm in eating or drinking other things.
واللہ اعلم بالصواب