This expression, which dates from the late 1800s, originally referred to the joint and limb aches experienced by youngsters who are growing rapidly. By about 1900 it was being used figuratively.
Problems that arise in beginning or enlarging an enterprise, as in The company is undergoing growing pains but should be viable by next year.
Emotional difficulties that occur during adolescence.
Problems that arise in the initiation or enlargement of an enterprise.
https://en.wikipedia.org/wiki/Growing_pains
