The key won't turn in the ignition. I think the cylinder might need replacing.
This seems to be a common problem on many vehicles. You can try to shake the steering wheel side to side while simultaneously attempting to turn the key. If this does not work some lubricant inside the cylinder may break it free. If none of these work, the lock cylinder is likely in need of replacement. Before purchasing any parts have the issue verified by a technician from YourMechanic. A professional diagnosis will always save you money in the end.