You need more privileges. Here is the minimal privileges for Nexus to manage s3 blob:
- ListBucket
- GetBucketAcl
- GetLifecycleConfiguration
- GetObject
- DeleteObject
- PutLifecycleConfiguration
- PutObject
You can using a user who has admin privileges to test this via CloudTrail’ log.
Here is the Official Docs: Configuring Blob Stores