It is possible that you might get an injury during the trek. It’s also possible that you might get sick. But if it’s a minor health problem which can be solved with less medical care then your guide will help you. With the help of a med kit, you can continue your trek.
However, if it’s serious then there will be a Helicopter evacuation. If you have travel insurance then the travel insurance will pay all the losses. That is why you have to do travel insurance also.