DL will almost certainly catch the MCT "violation" at some point and will, at that point, require rebooking. Far better to have that done now than later. There should be one later flight to OMA, so this should not be a major issue. But, as others note, look up the new flight number and call DL (or your TA if you booked through a TA), point out the MCT issue and then provide the specific new flight.