I hurt my foot four days back, and now it turns dark purple or black when it is not grounded. Why?

Hi doctor,

I am a 18-year-old and I hurt my foot four days back due to tumbling. I was doing a flip and landed in a pothole. My foot got hurt bad and I was able to ignore it. The next day, when I stepped down I got extreme pain and I still walked with it on that day. I went to urgent care after a day and the doctor told me that it was not broken and it was fine. But I was given an ace bandage wrap and I was on crutches. Yesterday, I noticed that when I keep my foot down during sitting in a chair or using crutches, my foot turned dark purple and my toes turned black. When I elevate it or without hanging it, the discoloration goes away. But today, my foot has fallen asleep more than ten times in an hour and I was not able to keep it awake. The color change is still occurring and it is cold to touch it. The other foot is warm. I am wondering whether it is normal for a sprain or should I need to look at it again.