Hello,
This brown spot looks like post inflammatory hyperpigmentation mark due to the dermatitis after using the dettol. The treatment for post inflammatory hyperpigmentation includes various skin creams like hydroquinone, azelaic acid, corticosteroids, tretinoin cream and laser treatment. But these are to be used only after prescription and examination from your dermatologist as it is not without side effects. If it still persists then you can go in for laser treatment, Chemical peeling or microdermabrasion.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
believe me it looks bad on nose
It is probably a scar, that will not go away, if it is not raised then it is permanent. But I wouldn't worry about 1 mark on your face, tons of people out there including me, are dealing with multiple marks on there face from post acne marks and unfortunately unless you have tons of money to get it somewhat fixed, then it's there for life!