Germs don't need much room to enter a body, just saying. So if the skin is broken, it's safer to do a mild treatment (Betadine or Vetericyn, etc) & easier than worrying about it.
Oh, & for a few scratches, I would NOT soak the snake. Just dilute some Betadine (if using that) & use a Q-tip to wipe it on the scratches, & hold him briefly while it dries. Soaking the snake is over-kill & stressful.