The Internet of Things (IoT) is rapidly becoming a common technology that will improve people's lives by seamlessly integrating into many facets of modern life and facilitating information sharing across platforms. Device Authentication is a significant challenge for IoT devices as they are placed in unprotected environments, vulnerable to physical attacks and common security risks. Large computational requirements and communication costs during Authentication make the existing methods, like Public Key Cryptography and Identity-based Encryption, unsuitable for resource-constrained IoT devices. Physical Unclonable Function (PUF) offers a lightweight security mechanism instead of traditional sophisticated cryptosystems by providing an unclonable and tamper-sensitive unique signature. Therefore, we use lightweight operations like bitwise XOR, hash function, and PUF, suitable for resource-constrained IoT devices to authenticate IoT devices. Despite several studies employing the PUF, to the authors' knowledge, existing solutions require an intermediary verifier/gateway and/or active internet by the IoT device to directly interact with a Server to authenticate itself and, hence, are not scalable when the IoT device works technologies like Bluetooth Low Energy, Zigbee, etc. To address the aforementioned issue, we present a system in which the IoT device does not require an active internet connection to communicate with the server. The results of a thorough security study are validated against adversarial attacks and PUF-modelling attacks. For formal security validation, the AVISPA verification tool is also used. Performance study recommends this protocol's lightweight characteristics. The proposed protocol's acceptability and defenses against various adversarial assaults are supported by a prototype developed with ESP32.