"If its outside the boat above the water line I’d put tape on the outside hole and patch the hole from the inside with thickened epoxy. Once cured, then prep the outside and match the Gel.
If below the water line normally you'd follow this step (patch size and glass type being variable). Prep a 2x2 area on both sides of the hole with 50 grit paper. Use two to four fiberglass patches starting at 1 inch and working up to 2 inches by the third patch. Repeat on both sides.
But with a hole that small, You could probably get away with a patch on the inside of the boat, especially if that area is unlikely to come in contact with anything. "
Stainless bolt (screw) of the proper size, 2 flat washers, and a Nylok nut. If it is indeed aluminum then insulate the added screw from the hull and use plastic washers. In either case use your favorite sealant.