Make some strong black tea in a stainless steel pan. Lemon balm apparently works too. Make it *really* strong. Boil it down until there's almost nothing left (but don't scorch it). Pour it into the top of a jar and leave it out to dry.
When the medicine is "fresh" (wet), you can stick a cotton swab into it. Dab the tea concentrate onto the sore. When the medicine is dry, use a wet cotton swab and rub it around until the cotton swab discolors (kind of like watercolors). Dab the tea concentrate onto the sore, as before.
This helps with pain, dramatically improves healing time, and is pretty non-toxic. Obviously, don't do this if you have serious allergies to tea or lemon balm. Also, don't choke on the cotton swab. I can't think of any other hazards.
Good luck!