No, you cannot sue the manufacturer for this. Blades used for food prepration are supposed to be sharp; there is no such as thing as making a blender blade "too sharp" and no fault (e.g. no careless or defective manufacture) for making it sharp. Furthermore, all you could recover in this case, even if there was fault (and so liability) would be the cost of the medical care, since "not getting your finger wet" is so minor an impairment a court would offer you little or nothing for it. Therefore, the lawsuit would almost certainly cost more than you could possibly recover from it.