Not urgent means...
The doctor is saying, "Don't worry, it's not dangerous.
I'll tell you if and when it's time to worry." Listen to the doctor (unless there is a valid reason not to listen to the doctor). Hgb is hemoglobin, and there are several types. If a child is growing and behaving fine, and already 5 years old, he likely has nothing urgent because he has lived happily with his hemoglobin type for 5 years.