HELP- What is this?

So yesteday when my baby woke up I noticed a little bit of a rash on her chest it wasn’t as bad as it looks today she doesn’t have a temperature or fever and seems well in herself overall. I’ve tried looking online but can’t seem to find anything it’s similar to. Should I be concerned and ring gp? I tried not to worry as she doesn’t have itchiness or temperature but seems to ha e got slightly worse