Urgent. My 15yo Sister Applied Cotton Pad Soaked With 4.8%

Urgent. My 15yo sister applied cotton pad soaked with 4.8% dettol and slept with it. Didnt realise this until she woke me up c/o of burning sensation. Told her to wash with water, burning sensation gone almost immediately. Then when i woke up this morning, only to realise its pink and almost dark over the whole area.
Any immediate treatment prior to waiting to be seen by dermatologist? Also, what is the prognosis of this type of burn?