Hi , L'm Had A Skin Graft Placed On My

Hi , l'm had a skin graft placed on my ankle about 20 years ago and 2 months ago I was hid by a rock pebble to that area. A week after I noticed some drainage coming from my ankle. To make long story short, the area has not heal and the wound has gotten worst. I have taken 2 different set of oral antibiotics and santyl. But the wound is isn't any better. There are sone spots of granulation tissue seen but the size is not decreasing. Please advice