Increasing pain is a sign of infection, and it is one of the few signs on every list of infection signs, whatever the wound type.
Increased pain is a sign of infection for venous ulcers, ischemic ulcers and diabetic foot ulcers. For surgical wounds, the sign is more redness or pain. Under a dressing, it is more pain. With cellulitis, it is pain or tenderness in the affected area, alongside a sore or rash that starts suddenly and grows quickly in the first 24 hours.
The word in each case is about change — increased, more. Not pain, but pain that has gone up.
That is worth stating because early pain is ordinary. A healing wound becomes slightly swollen, red or pink, and tender, in a stage lasting about 2 to 5 days. Tenderness at the start is part of the normal sequence. A rise after things had settled is not the same thing.
One kind of pain has its own instruction and sits above the rest: contact your provider right away for pain at the wound that will not go away, even after taking pain medicine.
There is also a pattern worth knowing that is not about infection at all. With ischemic ulcers, there can be aching pain in the foot or leg, often at night, which may go away when the leg is dangled down — and a leg that turns pale and cool when raised. Pain that follows position rather than time points to that kind of wound rather than to infection.
And the point that matters most for many people with wounds: in people with diabetes or pressure ulcers, infection may cause less obvious redness but more pain, swelling, or general illness. Where the visible signs are muted, pain may be the one that is not.