If it is dry and scarred then the wound seems to have started healing.
At this point, correct husbandry will be most helpfull and the snake will eventually shed most of the scar away.
If it still seems relatively fresh, polisporin once a day wont hurt but most likely won't do much. Making sure your snake has a nice clean environment would be best, I would suggest paper towels as substrate.
A good eye on humidity levels and making sure it's higher in shed phase is best.
Congrats on rescuing a BP and keep us posted
Pixie