At about 18:15 EST, a Piper PA-28-235 struck something shortly after landing at Raleigh-Durham International Airport. The airplane suffered a dented wing but the two occupants were not injured. The pilot said he made a visual approach to runway 23R and backed the approach up with the ILS. On touchdown the airplane veered to the left and into the grass. He stated he had not applied any brakes. He regained directional control and maneuvered the airplane back on the runway. He contacted the tower and informed them that he did not know what happened. The tower asked him if he had a bird strike. He looked out the window to his left and saw a dent in the wing, but so far the investigation has not determined what he hit.