"We could head to the tower to investigate" Major adds "however that is not our objective and it is clear that the information in there would not be of much use. I recommend we stay on course, it would not be wise to waste time and risk our safety if something were to happen." Major says as he walks beside Aukan and Stribog in an attempt to console them, informing them they are making the right choice.
As the beast tries to escape Major makes a quick swing to strike it (1d20 + 5 = 6 Critical Fail), the sword slips from Major's hands and the sword scrapes down his arm (damage 1/2 2d6 + 3 = 8 round up)
(I don't know what you want to happen different dms have different rules so I am just doing the standard I hit myself take half damage)
Major filled with adrenaline imedatly charges the already badly wounded displaser beast and strikes (1d20 + 5 = 8) missing the beast intierly. However Major quickly reacts to swing at it again (action surge 1d20 + 5 = 16) and this swing connects (2d6 + 3 = 12).