Shoulder injury related to vaccine administration (SIRVA) is a rare but preventable injury, resulting in severe shoulder pain. It is thought to be due to improper needle placement into the surrounding shoulder structures and can result in serious and debilitating injury. This case report describes a patient who developed a rare case of chronic inflammatory nonseptic monoarthropathy after combined influenza and COVID-19 vaccination. The diagnosis was suspected using point-of-care ultrasound, with findings of cortical erosions of the humeral head, which was confirmed with magnetic resonance imaging. After a primary autoimmune condition was excluded, the patient underwent ultrasound-guided intra-articular corticosteroid injection of the shoulder, which provided good pain relief. The role of ultrasound has not been reported in SIRVA-related conditions. Point-of-care ultrasound can potentially be useful in the evaluation and management of SIRVA-related shoulder pathologies.