I highly recommend going out and buying a hardwood board to start your first bows on while you wait for staves to dry. They are already dry so you could literally start working a board today and have a finished bow before the weekend is over.
Red oak is probably the most common, and its a great starting point. But you can find boards of cherry, maple, ash etc, and all can make good bows. Just make sure that the grain is as straight as possible. Straight grain is absolutely key for board bows. If that means walking out of the building supplied empty handed, and waiting a couple weeks for new stock, well so be it. There is just no way around it. Crooked grained boards will just be a source of frustration and discouragement.
Boards bows aren't usually as reliable as bows made from an actual stave like you have, but they are great for learning how to tiller, and to experiment on.
About the pocket knife, you could use that, but if you are going to get serious, you'll probably want a drawknife and a wood rasp. Luckily both of these things can be picked up pretty cheap, and they will make processing your bow much faster, and more enjoyable in my opinion.
