My 5 year old daughter became sick with a virus ( flu maybe) with a high fever , bad cough and congestion. She developed a hard, very painful white spot at the top of her lingual frenulum. After a couple of days, it came off in her mouth. I thought it was odd, but then her 4 year old sister caught what she had and now has the painful white bump on the same place, at the top of the frenulum under the tongue . What is this- I m sure it s from the virus, but it seems so specific under the tongue. There are not other white spots.