How to clean the wound from the finger with dry, black necrosis?

It is best to go with this type of case to a wound specialist (doctor or nurse). Treatment of this type of wound should take place under the supervision of an experienced person. Please look for the nearest wound clinic. If there is no one nearby - I encourage you to ask about teleadvice. Please do not remove this dry part "on your own". Improper removal of it (without consulting a qualified person in this area) and the lack of further appropriate treatment may cause another black necrosis to appear after some time. It is very important to do the right thing now. What I can advise at a distance is to relieve this place. A compressed wound may not heal despite the use of dressings and decontamination. If there is a possibility, it is also worth thinking about physiotherapy (if the patient is lying down) or movement (matched to the situation). Black, dry necrosis on the finger or heel may indicate circulatory problems, so it is worth contacting a doctor who will assess whether the treatment of circulatory diseases is appropriate (eg hypertension, coronary heart disease). If you suffer from diseases related to circulation, heart, high cholesterol or diabetes - I encourage you to exercise (eg walking, exercising at home) when possible. I leave a link to the text that may interest you: https://www.gdziepolek.pl/artykuly/problemy-z-sercem