How bad to mess up to get fired/disciplined?

Long story short, I’m a marine painter. I have restrictions due to having a ruptured disc in my back from work. So I’ve been assigned to jobs that accommodate that. Today I was assigned to paint walls in the office spaces for HR. I’ve never done house painting or anything. I received 0 training on this, was just told to paint the walls. The job doesn’t look great and there’s paint on the carpet. As a boss/foreman, is this something you’d fire an employee for? Or punish an employee for?