Are there any side effects for not treating a diabetic foot puncture?

Infection. . Diabetics don't heal nearly as well as non-diabetics, so even a very straight-forward puncture wound can become infected and cause major problems. See your podiatrist for wound care.
Diabetic foot. Any injury to the foot in a patient with diabetes needs immediate attention. Please seek help from a podiatrist or wound expert as soon as possible. You are at risk for an infectious process of the foot that will require diligence and careful followup. If the puncture was from metal and or outside, you also need to make sure that your tetanus is up to date also.
Failure to heal. A wound in a diabetics foot is serious. The longer it takes to heal the greater the risk of enlargement, tendon and muscle damage, worse yet, bone infection. In fact these may in turn make controlling your blood sugar harder as well.
Yes. Puncture wounds can lead of severe infections especially in diabetics. These infections could spread deep down to bone. If it gets severe enough, this could lead to loss of limb or even life. With puncture wounds, one may also develop tetanus. Often, people with numbness will delay treatment. Have the wound properly evaluated and treated to avoid preventable complications.
Infection amputation. Puncture wounds need to be cleaned and all foreign body particles must be removed from the wound to prevent infection. If left to fester, the area can become infected which can lead to amputation.
Yes. A diabetic can get an infection and an ulcer which could be extremely serious. I tell patients to inspect there shoe and don't walk barefoot.
Infection. If your are diabetic any puncture could become very serious quickly.