Most people have the opposite problem where the gear lever is too loose which indicates wear at the gear lever or the linkages. if it is stiff I would check to make sure the previous owner has not bodged a repair on the lever by removing the gear gator and checking the lever pivot and the bearing (plastic cup shaped thing the lever pushes into) at the end. Then I would have a check of the linkage under the gear shift under the car and also the one on top of the transmission these can get stiff (although most often go loose or wear out). Might just need a spray with lubricant.