There are two common explanations. The first is nerve damage, most often from diabetes. Diabetes can damage the nerves and blood vessels in your feet. This damage can cause numbness and reduced feeling in your feet. Diabetic ulcers are often painless, because of decreased sensation in the feet.
The second is depth. Deep wounds can affect tendons, muscles, ligaments, nerves, blood vessels and bones. A wound deep enough to involve nerves is a different situation from one confined to the surface.
Whichever applies, numbness is a risk rather than a relief. With reduced feeling, your feet are more likely to get injured and may not heal well if they are injured. If you get a blister, you may not notice, and it may get worse. The same is true with ischemic ulcers: nerve damage makes it harder to feel an area in the shoe that rubs and causes a sore. Once a sore forms, poor blood flow makes it harder for the sore to heal. A wound you can’t feel is a wound that won’t warn you.
It can be tested, and the test has a name. Your provider should check your sensation with a tool called a monofilament. Your foot pulses will also be checked. If your wound is numb and nobody has done that, it is a reasonable thing to ask for by name at the next visit.
One honest limit. Numbness isn’t on the usual list of changes to report, so this article won’t tell you that a numb wound is an emergency. But losing feeling isn’t a sign of improvement either. If a wound that used to hurt has stopped hurting, say when that happened and let the person examining it decide what it means.