What should I do about a vow to donate to Bosnia that I was unable to fulfill until the situation there changed and Islamic charities were fought against?

One must fulfill the vow and make up for any delay, as Allah Almighty says: "They fulfill [their] vows and fear a Day whose evil will be widespread." If it is possible to send the vowed offering to its rightful recipients in Bosnia, then that is obligatory. Otherwise, it must be sent to poor Muslims in other places similar to Bosnia's situation at the time of the vow, such as Palestine, Chechnya, Kashmir, and Kosovo.