Suggest Treatment For Spreading Skin Infection

I have been suffering from a skin disease for last 14 years. Its on my right foot, towards right hand side. Initially it started due to a insect bite, common in tea gardens. There was a small swelling like mosquito bite with a small blister. I was a kid, and due ti nail infection it spread like anything. After a long treatment (do not remember the medicines) the area of infection has reduced. But, still itching is there with a black covering over it. If sometimes I remove it, it gets watery with viscous liquid discharge. Recently it again started to spread. I consulted a local dermatologist and he suggested Halobet S ointment (Halobetasol Propionate - 0.5 mg + Salicylic acid IP 30 - mg). It is working well, but still need advice to remove it completely..