Most minor mishaps do not require any medical attention at all. The human body has its own way of dealing with them. In fact, often, administration of first aid by an over-enthusiastic elder can hamper the natural process of healing. For example, antiseptic creams often delay wound-healing while doing little to prevent unlikely infection. Sticking plaster can keep a cut unnecessarily soggy when exposure to air would have helped it to heal faster.
But then, probably your child would like you do something. He is hurt and he would expect you to give the wound the right amount of attention and not take it lightly. What you could do is wash the graze or cut under running water while you inspect it carefully to make sure that the matter is not more serious than what you initially thought it to be.
If the wound is actually minor, just try to make the child feel comfortable. Sit with him, tell him a story. There’s nothing like a few cuddles to make a frightened child feel better.
If you cannot decide whether the wound needs a doctor, take him to the nearest dispensary. Let the nurse decide whether he needs one.