Cleaning nipple piercings

What can I use to clean my nipple piercings?? They’ve been pierced for almost a year but I think they’re getting infected. Can I use peroxide? I think I remember the piercer telling me not to use peroxide but I’m not sure if he said that because they were new piercings.

I’ve been hitting my nipples a lot by accident and I have brittle diabetes so I think that’s why they’re getting infected but I’m not entirely sure.