All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
You did not clarify to us clearly on what matter you made your vow and the reason that pushed you to make this vow, and your age when you made it. In any case, if you were below the age of puberty, then your vow is not effective and it is not an obligation to fulfill it because among the conditions of the vow being effective is that it should be made by a pubescent and sane person, and the vow of a person who is below the age of puberty is not effective; for more benefit on the age of puberty, please refer to Fatwa 83431.
However, if you were pubescent when you made the vow and you vowed to do a permissible act of worship which is not obligatory in principle –like performing a specific number of Nafl prayers (supererogatory prayers) –and you conditioned that on the occurrence of a specific matter, like having a problem solved and so forth, then this a conditional vow and it is an obligation to fulfill it when the thing upon which you conditioned the vow happens. In which case, you should pray until you think that you are acquitted from the vow obligation.
As regards your statement whether or not there is an alternative for this, then you did not mention to us the reason why you made the vow and its kind, so that we may know whether it is among the vows that can be replaced by expiation, or that it is among the kind of vows that must be fulfilled and which cannot be replaced by expiation.
For more benefit, please refer to Fatwa 84107.
Allaah Knows best.