The easiest solution is to break out the nail glue and a tea bag (Crazy glue can also be used). This allows you to keep the nail in tack while it grows out past the point of the breakage. Start by cutting off a small piece of the tea bag. It should be large enough to fit over the crack. Then, add some nail glue to the paper and press it on to your nail. Once the glue is dry, file down any rough areas before applying a top coat to protect the nail. You can then apply your favorite nail polish and an additional top coat.