I Am A 60yo Male. I Had Surgery On My

I am a 60yo male. I had surgery on my head 2.5 weeks ago. 1 week ago my left thigh started getting very painful, it is swollen, painful, cool to the touch, and when I sit down, it feels like it is pulling on the front of my thigh. I did notice today, there are some bruises that have developed on both sides of my knee, but they are not painful. Can you help me figure out what's going on with my thigh<