Why Hasn’t My Black Locust Thorn Wound Healed After A Year Of Treatments?

leg got pierced by a black locust thorn ...lower front of leg been getting treatments from a dermatolist for 6 months,... no improvement went to a wound treatment center for next 6 months very little improvement...still have pain from a quarter sized hole left by treatments...no one seems to have an answer..... whats your thinking?