Instance in AWS Lightsail

One of my instance in AWS Showing errors

A PHP Error was encountered
Severity: Warning

Message: fopen(/tmp/ci_sessionrr5siklt0lkk24ufj0dmb3lqncmnflcf): Failed to open stream: No space left on device

Filename: drivers/Session_files_driver.php

Line Number: 174

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A PHP Error was encountered
Severity: Warning

Message: session_start(): Failed to read session data: user (path: /tmp)

Filename: Session/Session.php

Line Number: 143

-----------------------------------------------
Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once