Last week my doc says i have a small fracture of the radius in my arm, but i don't have any more pain, could it have healed in one week?

No: It may have been your growth plate scar they were looking at. Hard to say without seeing your x-rays.

Many small nondisplaced: Fractures may only hurt for short time but part of the reason why they stop hurting is because they're being treated properly depending upon location one may treat a different time intervals small minor fractures of the radius at the elbow may only need a week of a sling while others at the risk may only need us splitting a casting for a few weeks but it is very specific to the fracture not the location only and others take much longer to heal.