Hi Satinder,
Thank you for your message. The Sonatype Nexus Repository HA Operator starts in OSS mode by default. However, as explained in steps 3 to 14 of documentation you have to create a Custom Resource and specify additional details including your Nexus Repository Pro license. If you have a Nexus Repository Pro license please contact Sonatype support support@sonatye.com for additional assistance.
Kind regards
Olu Shiyanbade