It is worth pointing out that the vow concerns a business transaction.
All perfect praise be to the Lord of The Worlds.
If what you have uttered wasn`t in the form of an oath and you didn`t specify a certain act of worship in your vow, such as saying: "Allah is my witness that I won`t do so and so, then you aren`t obliged to offer an expiation.
However, if you made an oath to quit something or took a vow where you said: "Allah is my witness if I do so and so, I will draw closer to Him by performing a certain act of worship", but you didn`t fulfill either of them(vow and oath), then you are obliged to offer an expiation which is feeding ten needy persons, a Mud for each (a Mud`s cash value ranges from half a JD to a JD), or clothing them, but if you couldn`t then you could observe fast for three days. This because, according to Muslim jurists, this vow is known as "Lojaj" i.e. "Vowing to prevent himself o someone else from doing something or encouraging himself or someone else to do something, while in a state of anger, is associated with commitment to offer an act of devotion." Allah's Messenger (PBUH) said: "The atonement for a vow (Nadhr) is (the same as) the atonement of an oath (Yamin)." {Reported by Muslim}. And Allah Knows Best.