"Wind" can be pronounced with the [i] sound or the [ai] sound. However, these are two entirely different words. Wind [i] = a noun; a movement of air Wind [ai] = a verb; to make a rotating motion. It takes an object, such as a clock spring, or thread/string. As for the difference in pronunciation... well, you'd just have to look at the history, if you're interested.

You are correct about the general rule, but note that this only applies to single syllable words: window, tinder, for example, are pronounced with the [i] sound. Note also that 'wild' has the [ai] sound , but 'wilderness' has the [i] sound.