(SFGATE) — Courtney Withorn began biting her nails as a teen, after facing torment from bullies at school. The habit became so severe at one point, that she nibbled off the thumbnail completely.

Earlier this year Withorn, a 20-year-old psychology student from Australia, noticed the skin under her nail turning black. In July, doctors diagnosed her a rare form of cancer, reported British news site, the Sun. They were forced to amputate her thumb after multiple surgeries.

“I can’t even explain how self-conscious I was. I always had fake nails to hide it because it was so black,” she said, describing how she kept her thumb hidden from her friends and family out of embarrassment.