Red sore itchy lumps on legs, feels like a bruise

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This started about last October, I noticed I had a sore red lump on my right shin and expected it to turn into a bruise and go away. The lump turned into 2 or 3 smaller lumps that would move. It wouldn't move quickly but the lumps would usually be in a different spot after a few days. When it didn't I saw a doctor in December and got an x-ray and ultrasound, which my doctor said came back as normal. The lumps are gone but I still have dark spots where the lumps were.

Now I have the same on my left leg right under my knee. Very sore and sensitive. Red and itchy at times. The lumps are usually in a slightly different spot every few days. Any ideas what this could be? My doctor wasn't worried when I went for my other leg so not sure I want to waste my time going back again.