What are the serious signs of infection in your body?

Sounds a lot like an abscess that needs to be drained. Seek medical attention immediately but in the mean time do hot and cold compresses.

This person should go to the er immediately. The knots will only continue to grow and get worse. They need to be surgically opened, drained, cleaned and packed with medication. Left unattended they can progress to the point of amputation being the only recourse.