Let it stand overnight. You can also shrink your scabbard if you soak it in water and then wrap it tightly with a belt or piece of rope. Let it set overnight. Today there may be better products but old habits have a way of staying with one. This is the new HI super frog.
Top pix is the basic toolkit of the sarkis.
Bottom is the BirGorkha heavy duty sewing machine. Seated at the machine is sarki Govinda. This is a scabbard Terry Cisco made for a khukuri that John Powell picked up somewhere. Terry started from scratch, fashioned the wood portion of the scabbard to fit the blade and then covered it with leather as shown. So, if anybody needs a custom traditional scabbard you can check with Terry at the address below, or at his webpage .