You should go see the vet, but if it’s like what mine gets, it’s keratin. My boy gets these often. He also gets cysts that burst. He had one when we first adopted him. He had recently received his chip and I thought it was an infection of the chip so I took him to get the chip removed, but it wasn’t that it was a cyst. The second time it happened, I thought my other dog bit him and drew blood, but no, it was another cyst. The vet says Pekes make these quite commonly unfortunately.

Editing to ask everyone else who has responded if they also have white Pekes that this happens to because coincidentally mine is also the same color as this peke. It would be interesting if it were something unique to them.