Wart on cockatiel's beak? Please help

Hello! I have 2 loving cockatiels. One of them - 15 years old male have something like wart on down part of his beak. He's molting now too. He's acting and eat normal. I thought that his beak had injured somehow, maybe when he was eating wall. One week before his beak look diffrent. Yestarday this bump was little bleeding. What can it be?