How common is mastitis with nipple piercings?

Ok so let me start from the beginning. Me and my best friend wanted to get our nipples pierced for his 21st bday. We did. I had NO clue you could get mastitis or anything like that. Well my dumbass let my ex put his mouth near the piercings... I cleaned them directly afterwards and always got rid of the crust if I saw any.

Well, 7 months later and they still have pus. I've been soaking them in seasalt once a day at night and really making sure all of the bacteria is out. I even move the bars back and forth to make sure none is trapped in the hole itself.

How much am I at risk of mastitis? And also, could nipple piercings affect the whole boob itself if the piercing is infected?