Final answer:
Of the provided assessment data, a nontender axillary lump would be of most concern as it could indicate a malignancy or serious infection, requiring immediate attention for an immunosuppressed patient.
Step-by-step explanation:
The patient in question is receiving immunosuppressants such as tacrolimus, cyclosporine, and prednisone following a kidney transplant. Of the assessment data provided, the most concern for the nurse should be Option C: A nontender axillary lump. As an immunosuppressed individual, the patient is at higher risk for infections and cancers; a new lump could represent a possible malignancy or a lymph node responding to infection, which requires immediate attention. While Options A (skin is thin and fragile) and D (blood glucose is 144 mg/dL) can be related to the side effects of the steroids and immunosuppressive therapy, and Option B (blood pressure is 150/92) is hypertensive, these conditions generally do not require the same level of urgency as a possible indication of cancer or serious infection.