I do not know what they learn, but they might learn about the illness as a deviation and about the relation between patient and doctor in the light of functional theory (Talcott Parsons and Robert Merton)

Asylum, Erwing Goffman

What are some important sociological theories and concepts that nursing students at the Bachelor level need to learn which can be useful in practice?

Students at the Bachelor level need to study medical sociology, through which they understand the relationship between society, health and disease and will find all social concepts and theories useful in practice.

He can also study medical social service, as it provides him with the skills of practicing service in nursing, and thus the nurse will learn to take into account the psychological and social aspects that make the patient happy to recover from the disease.

Conflict theory

These are some very useful sociology references:

cognitive theory, Social Learning Theory

They need to understand complexity theory

I'd encourage social psychologic theories/frameworks as they are easy to understand and leverage. Two examples include:

Theory of Planned Behavior: There was a recent paper that reexamined the Theory: The Theory of Planned Behavior: Selected Recent Advances and Applications - PubMed (nih.gov)

Transtheoretical Model: The transtheoretical model of health behavior change - PubMed (nih.gov)

A broader medical sociologic theory - The Fundamental Cause Theory is informative on broader issues related to agency in managing health risks: Social conditions as fundamental causes of disease - PubMed (nih.gov)