My son is 10 years old and is a little over weight and his blood sugar level was just 138 is this to high?

Overweight. If you took a fasting blood sample, myou should definitely have your son evaluated for diabetes.
Yes indeed. I also see that somebody is on Insulin already. Is this you? If junior is not already diagnosed with diabetes, he needs to be rechecked and he needs to get physically fit. This could be a great project for your family.