My son is 7 years old and taking antibiotics for an ear infection. Yesterday I noticed a sore in his mouth, and today this sore has turned white and has a velvety texture to it. He also has quite a bit of swelling in the cheek where the sore is. From what I have seen, it definitely appears to be thrush, although I'm not sure about the swelling. Can I treat this at home, or is this something I should have checked out by a doctor?