For medical DIY - if it's nothing too serious - cyanoacrylate-type instant glue will seal minor knife cuts almost instantly.
Make sure the wound is clean and it'll heal nicely without scars too.
Use self-adhesive bandage to relieve tension on the wound and the glue.
I used to do some scale modelling, so cuts were more or less unavoidable, and I always repaired them with what I had at hand : CA glue
It has been or still is being used in the medical world to close clean scalpel cuts.