Big blister on heel with black around the edge

Basically a week ago I went for a 4 mile walk in the wrong shoes, and a couple days later I started getting a pain in my heel and I couldn’t walk on it or anything because it really hurt, so the next day I went to the doctor and they said it was a deep blister under my callus on the bottom of the heel so I wont be able to walk on it until its heeled or something like that, and today 11 days after the walk and a week after the doctor I have a huge blister that takes up the curve of my heel so I cant walk on it in case it pops and its started to get black around the edges so what do I do? Do I pop it and risk infection or stab a needle in it and let it drain or what?

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Big blister on heel with black around the edge

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