Should I retake a day of fasting in which I did not sleep next to my husband after our dispute, knowing that my fast was obligatory, not supererogatory?

You are not required to make up for this day, as estrangement does not invalidate the fast. However, it is important to know that it is not permissible for a woman to abandon her husband's bed without a valid religious excuse. You did well by reconciling, and sincere repentance is obligatory.