Got A Wound On My Leg Caused Due To An

Got a wound on my leg caused due to an accident,the whole skin is peeled off the wound does not looks to be that deep.But over 20 days have passed but the wound is still not healed though a scab is formed which turned into black from light yellow i have severe pain and difficulty in walking, xrays taken but no fracture found.Arthopaedic alos ruled any ligament or muscle tear.I have applied soframycin,silver cologian gel,also taken oral ampicillin of 500 mg and harpagoside bromelain trypsin and also wash my injury twice a daily with soap water and dettol.I have checked my sugar level which is normal.I want to know why the process is taking so long.