Pus is one of the signs of infection. Whether it always means infection is a fair question, and the first step is being clear about what pus is, because the word is used loosely.
Pus coming out of the sore is a sign of infection for a pressure sore. Pus is also a sign of infection for a diabetic foot ulcer. For any wound, contact your provider right away for redness, increased pain, or yellow or green pus. These are signs of infection.
For a surgical wound, contact your surgeon if the drainage coming from or around the incision increases or becomes thick, tan, green, or yellow, or smells bad. That cluster is what pus means.
So pus is drainage that is thick and discolored and often smells. Not any drainage, and not any color.
That matters because some drainage is expected. In the early days of healing, some clear fluid oozes from the wound, and this fluid helps clean the area. Part of a dressing’s job is to soak up any fluids that leak from the wound.
Pus is different. It is not treated as harmless or as a normal stage of healing, and there’s no reassurance to offer about it.
The practical reading: drainage that has become thick, changed color to tan, green or yellow, or started to smell is something to report — whether or not you would call it pus.