Oh no. I can't think of any small knives showing up in the original trilogy (there were spears, axes, and other melee weapons though), but I don't think that was out of any kind of ban.

In a lot of legends material, there are knifes being used. In the Thrawn books, which are some of the establishing EU, an officer under Thrawn has his throat slit in front of the crew. Visual depictions of knives, especially vibroblades could be found in games like Knights Of The Old Republic, and Republic Commando.