His blood sugars have been under pretty good control and he has no known complications at this time. Individuals with diabetes can get many kinds of foot problems. Even minor ones can quickly turn into serious ones. You mentioned that your son has developed a corn and calluses.
Calluses are areas of thick skin caused by regular or prolonged pressure or friction.
A corn is a callus on a toe. Corns and calluses can develop on an individual's foot when their body weight is distributed unevenly. Calluses and corns should be trimmed by your son's health care professional. Trying to cut corns and calluses on your own can lead to infection. Untrimmed calluses can get very thick, break down, and turn into ulcers.