Okay Momma's I need help. Baby girl has this thing on her chin that's been there for about 3-4 days…

Okay Momma's I need help. Baby girl has this thing on her chin that's been there for about 3-4 days now. At first it just looked like a raw spot which she drools REALLY bad 24/7 so I've been keeping it as dry as possible but it's not getting any better. It doesn't look a lot worse but it's enough to have me freaking out a little bit. She had a heat rash yesterday under her chin and on her neck and chest a little bit and she has a little bit of baby acne or heat rash on her face most of the time that I've asked her pediatrician about but I've not made an appointment for this yet.. what could this be? In the pic in the right corner she has a little spot that looks similar to it on her neck.. she's been acting like her normal self and it doesn't seem to bother her if you touch it or anything but I am in a panic over it.