Worried? No, conscious? Yes. If you’re using a full frame sensor lens with a crop sensor camera, the image will be cropped by your camera sensor.
This means your lens’ “equivalent focal length” will be longer than its true focal length. This happens when mounting a large sensor/full frame lens on a camera with a smaller/APS-C sensor camera. The camera will apply a crop factor in the lens field of view, which will make the image appear more zoomed in that it did through your viewfinder.
Here is an analogy to help you think of this in a different way: Imagine you have a projector and it’s set up to create an 8×10 metre image – this is your full frame lens. But you only have a projector screen that is 6×8 metres (this is your APS-C sensor). The screen you have to capture the image is smaller than the image itself, so you can only capture a smaller part of it – your image will be cropped.