The idiom is often used in a humorous way, but it can also be used to describe a more serious situation. For example, a dog with a bone might be someone who is holding on to their money, even though they desperately need to use it.
Dogs are known for being playful and affectionate, but they can also be fierce watchmen and protectors of their territory. When a dog has something in its mouth, it may feel that its possession is threatened and may resort to defensive behaviors, such as growling or even biting.
The idiom dog with a bone is a reminder that we should learn to let go of the things that we no longer need or want. Holding on to things can weigh us down and prevent us from moving forward in our lives.