Hi @beryour ,
Do you mean the rear facing camera?
If you do, then perhaps the camera is faulty and needs to be replaced.
Here is a link to a video showing how to dis-assemble the phone. At 9:08 minutes into the video the rear camera can be seen being removed.
Here is a link to suppliers of the part. It is not a recommendation to use them. It is shown to give an idea of the cost of the part. There are other suppliers online who may suit you better. Just search for Sony Xperia Z1 rear camera part to get results.
If you do decide to replace the camera remember to disconnect the battery as soon as you can before removing or touching other parts with tools etc. The systemboard has still got power on it even though the phone is off. You don't want to cause more problems that what you've already got.
Basic rule in electronics repair - power off first, on last