Though I'd jump in with some additional thoughts on  Healing sore nipples.
The comments on hydrogen peroxide are somewhat surprizing. The harsh reaction
when it is poured on a wound can cause some of the cells that are attempting
to heal the wound to necrose or die and can damage healthy tissue. A plastic
surgeon once told me he'd seen more damage from people using hydrogen
peroxide to clean the wound than the initial wound. The necrotic sections had
to be cut away before he could suture. The end result was a nasty, often
deep, scar.
Wound healing occurs in several ways:
First intention or primary union; where the skin edges touch each other. (a
surgical wound or a paper cut) The wound heals from side to side.
Second intention or granulation; The wound is open and the skin edges do not
touch each other. (Scraped knees, and deep nipple fissures) The body forms
granulation tissue that fills the wound. Basically the wound heals from the
bottom up. The more vascular the area the quicker the healing. Granulation
tissue is very sensitive and bleeds easily.
Third intention or secondary suture; The wound is left open to begin
granulaton then the two edges of granulation tissue are brought together and
 sutured. This is usually done for large wounds.