Hi@akhtar,
Terraform has resource to create a secret in Kubernetes Cluster. You can use the resource and pass your credentials as shown below.
resource "kubernetes_secret" "example" {
  metadata {
    name = "example-test"
  }
  data = {
    username = "admin"
    password = "GuessPassword"
  }
  type = "kubernetes.io/basic-auth"
}