When a bottle of sterile water/sodium chloride is opened to clean a wound, is it still considered sterile?

I am an LPN who recently got laughed at at my previous job at a clinic because I had been throwing away the sterile water after a procedure, which is what I have always done & what everyone else had done at my previous job in a hospital. I said if we are going to keep the water for later use we at least need to date the time the bottle was opened. I was taught in school that bacteria grows on open containers even after they are shut and this would no longer be considered sterile. I am just looking out for my pt's and the company. I am no longer at this place of work-but want to know the right answer when it comes to sterile procedure. Is it different in the hospital than in a clinic? And why? Sterile is sterile and an infection is an infection. I just want my patients to be healthy.