@Vishal Gupta
Please try this.
Change your Tomcat port to 9090 (instead of 2222) and then try again
9090 is the defauilt Nifi Port , which might not be running on your Sandbox and the port forwarding rules are already setup for port 9090 so you should be fine with this port.
Change the tomcat port to 9090 and then restart the tomcat then try accessing the tomcat URL on this port.