Rash on baby mouth help!

My son is 6.5 months old and he has a rash under his mouth, at first I thought it was just dry but I am not sure. He just recently started using his pacifier a lot more than he used to so idk if that could be it? I tried putting breastmilk and keeping it dry and I was now considering coconut oil...should I take him to the doctor? Help ftm and I can't stop worrying that something is wrong . Plus he is a drool monster