@melissa, first welcome to CCF. Second, it is a little hard to see from your pics whether this triangular section is recessed, proud, or flat with the rest of the fields of the coin. Your last pic is about the best one and in this it looks like this section is level. In that case, that groove, which starts on one rim and then proceeds over various design elements before returning to the rim is most likely damage (not a mint error).
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