Not to brag, but I finished the project early.
not to brag
idiomPrepended to praise of oneself or one's own doings, as a form of modesty.
Origin
disputed originA reference to the fact that the speaker is about to say something boastful rather than modest.
Not to brag, but my garden looks better than it ever has this summer.
Not to brag, but the committee selected my proposal over dozens of others for its unique approach to the problem.