please help:( I feel so bad

okay so I’m gonna try and keep this short and keep my anger out of it. I’m going anonymously because I don’t want to throw any hints at anyone particularly. But we were at my friends the other night my 14 month old son and I, basically the day was rough, and I didn’t wanna stay but my boyfriend knew I was too tired to drive home after my training and convinced me to stay. I love her as a friend but I will admit that she is not a clean / germaphob like me. And I have now found so far 3 lice in my baby’s hair😭😭😭 please tell me what to do, I feel so awful I feel like I’ve failed him myself. I saw fleas and stuff on her pets but I just kept him away, I didn’t expect my son to get lice :(( what do I do? I’ve never experienced this before