Welcome to BYC. Yes that is bumblefoot. I usually only do the surgery if my chicken is limping, or it looks red, swollen, and has the dark spot. Sometimes there can also be swelling on top of the foot between the toes. Let us know if you would like to read some info or see videos of the surgery.
Some people soak the foot and can pick off the scab and massage out the infection. Here is some good treatment info: