Traditional standards and security protocols are recognized as unable to solve the security, privacy, and availability of services of the Internet of Medical Things (IoMT) ecosystem, especially during the Coronavirus (COVID-19) pandemic. Blockchain technology has then emerged as a distributed ledger technology that can manage many intelligent transactions and ensure greater security in data management. The Blockchain-based security mechanisms with specific adaptation and additional layers of authentication and verification can offer a complete resources' management system. It has demonstrated it’s superlatively as the core component of the Bitcoin cryptocurrency. In this paper, we propose a ThreeTier Blockchain Architecture in a hierarchical clustering network, with a lightweight authentication system-based API Gateway model that provides network and communication security. Reasonable implementation is proposed and the obtained results demonstrate that our approach shows satisfactory performances in terms of transfer time, energy consumption, and CPU impacts. The traffic analysis also shows that the proposed model can meet the requested security, integrity, and confidentiality of user data.