When you first start using a massage gun, it is normal to feel a little bit sore afterward. This is because your muscles are not used to the deep tissue massage that the gun provides. However, if you find that you are feeling extremely sore after using the gun, then you may be pushing too hard or using it for too long. Remember that the goal is to relax and feel better, not to suffer. If you have any concerns, consult with your doctor before using a massage gun.