What Causes Dark Bruise In Inner Thigh And Right Shoulder?

I have noticed in the past 3 days I have a new bruise. I on each inner thigh very dark almost black in color and the one today in on my right shoulder, the color is red & purple and feels like a knot is in it. It is sore to the touch. The two on my inner thigh have no pain. What could cause this & should I go to ER since my PCP will not be back on office until Monday? I am a 58 yr old women with numerous health problems.
Thanks