Hello Firstly do not worry about it. It seems to be a small injury with normal amount of swelling causing the bump. And it has been cleaned well. Since it is quite fresh the black maybe due to dried blood. Make sure there are no debris/sand etc from the ground in the wound. The surrounding skin maybe dark because of underlying bleeding or a clot forming. This will fade by itself. In case of any pus or fluid discharge/ swelling persisting get it dressed at a clinic. Apply an antiseptic ointment such as povidone iodine with a light bandage.