Is my cut healing properly?

about three weeks ago i stepped on a broken beer bottle & cut myself on the bottom of my foot. I made the mistake of going to the hospital till the next day but after all I ended up getting 9 PAINFUL stitches on the bottom of my foot. After 2 weeks with them on I went to get them removed & they told me to stay off it for a couple more weeks. My question is if its normal for my whole foot to turn purple while i have it down? if i am laying down there seems to be no problem but as soon as im on my feet using my crutches or sitting my foot starts turning a bit darker, theres no pain, heat, or coldness should i be concerned?