After Breast Cancer Surgery I Got Lymphedemia In My Right

After breast cancer surgery I got lymphedemia in my right arm. Have dealt well with massage therapy, but two days ago I found an ugly blackish green circle surrounded with redness with no open sore. This morning I found a discoloration (like a black and blue mark) on the back of my hand near my wrist. It has a small soft knot in the middle. No trauma has happened to that hand and arm and it does not hurt. Any ideas what this might be?