The stitch is basically put where there was a cut. When they say stitch can be removed in 7 days, it means it takes 7 days for the cut to heal and connective tissue to grow and connect the two sides and oppose the cut surface together.
Therefore, it's important you keep the area clean. Bacitracin is antibiotic will prevent growth of bacteria. It's important you apply it twice daily on stitch area. Its better you keep away from swimming for 7 days. Water is chlorinated and there could be other microorganisms growing in water.
Try keeping it dry and not wet to prevent yeasts growing too.