I have a django application where one application has many-to-many relationship with a UserProfile. But whenever I do a syncdb, it warns me that app_users is stale field
Pay attention to the message. It's not claiming that your field is stale - it's talking about an entry in the Content Types model.
In the shell, do this:
from django.contrib.contenttypes.models import ContentType ct = ContentType.objects.get(app_label='Apps', model='app_users') ct.delete()