This is likely a result of winter sunscald which affects thin-barked trees and typically shows up during late winter. When we experience warm winter days, the sun heats up the tree, usually on the south or southwest side of the trunk. This causes the cells on that side of the tree to come out of dormancy and become active. If the temperature later drops to freezing, it can damage or kill those plant cells causing the tissue to become sunken. The damaged bark will begin to crack and fall away over time.
The best solution to this problem is prevention. A variety of wraps are available to protect the tree trunk. Trees that show symptoms of damage should be monitored for pests. Provide proper care to prevent further stress.
https://hnr.k-state.edu/extension/horticulture-resource-center/common-pest-problems/documents/Sunscald%20on%20Trees.pdf