Do you have a hardware firewall? If so I wouldn't worry about it. Most consumer home 'routers' have such a feature. And in my experience that's going to stop anything you'll casually have thrown at you. The only issue with not having a software firewall is no control of outbound data but to some degree if you're running anything truly malicious and untrustworthy unless you're running it with limited permissions or virtualized you're already fucked.