The most important thing is to make sure it does not get worse and starts to heal. Healing can take a long time depending on how bad it is. You can increase the temperature and add salt like was suggested. I would also recommended you turn off the light and make sure they are comfortable and not stressed.
Clean water, salt and no stress go a long way to heal a lot of wounds. The picture doesn't look horrible and like something that can heal. You just need to make sure it does not get worse.