Humans can make mistakes and lie, and we've been able to deal with it by checking their work, giving feedback to help them improve, placing less trust in those who habitually lie, etc..

LLMs making mistakes and "hallucinating" can be dealt with in similar ways, and as this is an open area of research with lots of proposed solutions and probably many more in the years to come, we do/will have plenty of other ways to deal with it too.