What should we do concerning the vow we made to ourselves to recite Surat Al-Baqarah daily, which we have not fulfilled?

Merely agreeing to recite a Surah does not entail any obligation. However, it is recommended to strive diligently in reciting the Quran, memorizing it, and acting upon its teachings. If, however, the agreement was made through a vow (nadhr) or a covenant with Allah the Almighty, then fulfilling the vow is obligatory, and any missed recitations must be made up.