My MIL was putting our 4 month old in the car and strapping the car seat in and she said the seat belt slipped out her hand and the metal bit hit front of babies head by accident and has left a little red mark! She feels terrible and has been crying, I am no way angry at her as accidents happen and my baby is smiling, giggling and feeding fine! Is there any reason for me to be concerned? First time mum here is it obvious?!!