Final answer:
The most appropriate initial nursing intervention when assessing a client with a soft and boggy uterus in the immediate postpartum period is to massage the fundus until it is firm.
Step-by-step explanation:
When assessing a client in the immediate postpartum period and finding a soft and boggy uterus, the most appropriate initial nursing intervention would be to massage the fundus until it is firm. Massaging the fundus helps to stimulate uterine contractions and promote involution, which is the process of the uterus returning to its pre-pregnancy state. By massaging, the nurse can encourage the uterus to become firm and prevent excessive bleeding.