self-flattery; singing one's own praises
Used when someone boasts about themselves or their own work, often with a self-deprecating or critical tone. Common in set phrases like 手前味噌ですが (though this is self-praise...).
Though it's self-praise, I think this project is well done.
彼の話はいつも手前味噌で、聞いていて恥ずかしくなる。
His stories are always self-flattery, and it's embarrassing to listen.