A 67-year-old man presents with frequent headaches for the past month that localize unilaterally to the left temple and occasionally radiate to the left eye. He has associated symptoms of fatigue, involuntary weight loss, and pain with chewing. His past medical history is significant for hypertension. Current medications include lisinopril. On physical examination, a small knot-like swelling is palpable on the left temple, and it is tender. Laboratory results show: Hemoglobin 12.9 g/dL Hematocrit 40.7% Leukocyte count 5500/mm3 Neutrophils 65% Lymphocytes 30% Monocytes 5% Mean corpuscular volume 88.2 μm3 Platelet count 190,000/mm3 Erythrocyte sedimentation rate (ESR) 95 mm/h What is the next best step in the management of this patient?