On average, how long will an eraser burn take to heal?

Care=Healing. Burns are response of tissues to injury. It is simply inflammation which means increase blood flow to the area to promote healing. Depth determines care. Ice worsens already injured skin. Cool water soaks help also anti-inflammation medicines like Motrin or advil (ibuprofen). Avoid any further damage as this can cause scarring . Good skin cream applied daily/gently help unless deeper then seek help.