Go to the town with the Fighting gym. In the cave there, on the lower levels, there will be rocks you can break with rock smash. Break those and, if you're lucky, a Nosepass will appear to fight you. Be forewarned that it is not guaranteed that a Pokemon will appear, and if one does then it will most often be a Geodude, but this is the only way I know to get a Nosepass if all you have is Sapphire.lol