I had one in the 60s and had to have it lanced. My thumb was about 3 times normal size but once lanced - instant relief. It’s said to be something only experienced by males in index fingers and thumbs. Something to do with bone structure in the phalanges ? Incidentally ,(and no help at all ) a whitlow is how my Mum and Dad met. She was his superior when he went into the RAF in WW2 as a raw conscript. He was taken to see her because he had a whitlow and she knew what to do. He fell in love with her , instantly, and they wed, less than a month later, staying married until he died 48 years later.