You can also use the direct deploy method using curl. You don't need a pom for your file for it but it will not be generated as well so if you want one, you will have to upload it separately.
Here is the command:
version=1.2.3
artefact="myartefact"
repoId=yourrepository
groupId=org.myorg
REPO_URL=http://localhost:8081/nexus
curl -u nexususername:nexuspassword --upload-file filename.tgz $REPO_URL/content/repositories/$repoId/$groupId/$artefact/$version/$artefact-$version.tgz