Today, I attended mass at a church that isn’t my home parish. I received in the hand. I believe I took a step to the side, then consumed it. At some point, I spotted a small white flake in the air, falling to the floor. I wasn’t sure if it was a crumb from the Eucharist, or something else. In retrospect, it seems obvious that it was a crumb. Not knowing what to do, I went back to my pew. Is there something that I should have done? Was this sacrilegious? Do I need to go to confession?
Seeing that you’re not even sure if it indeed was a piece of the host you did not sin. You obviously did not intentionally or carelessly walk away from a piece of the Eucharist.
Even though the Real Presence is fully present when the host is broken into pieces, that does not mean it is always the Eucharist.
Catechism of the Catholic Church [emphasis added]:
1377 The Eucharistic presence of Christ begins at the moment of the consecration and endures as long as the Eucharistic species subsist. Christ is present whole and entire in each of the species and whole and entire in each of their parts, in such a way that the breaking of the bread does not divide Christ.
This means that Jesus is truly present in the Eucharist, so long as the Eucharist retains the actual accidents of bread and wine. If a “fleck” of the host is so small as to be unrecognizable as a form of bread or even as a crumb of bread then it not Eucharist and does not contain the Real Presence.