Per the DNA painter tool:
84.69% probability that it is one of the following relationships:
Grandparent, Aunt / Uncle, Half Sibling, Niece / Nephew, Grandchild
With that amount and not matching your aunt, the match could be through your other parent. Or this could be a half sibling. How much do you know about both your mother's and father's relatives? Families do lose touch or even disown family members. Then people don't even know some of their close relatives.