Distinguishing between the camera lens and the lenses inside the camera lens

Solution 1:

From Wikipedia

A camera lens (also known as photographic lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects ...

If camera lens / optical lens is not a sufficient distinction, you could call the whole thing the assembly and the individual parts elements (some may be mirrors) if you need to be particularly clear which you are talking about, provided it is already clear you are considering camera lenses.

Solution 2:

A camera typically has a compound lens, which is an assembly of individual glass lenses that are arranged in a particular configuration to focus light. The whole lens assembly may be correctly referred to as simply a lens, since the whole apparatus is just a device that focuses light.

The term lens element may be used to refer to any one of the individual glass lenses that make up a complex lens. A high-end photographic lens may consist of a dozen or more lens elements.

See Lens Elements at Wikipedia.

Solution 3:

They are known as "lens elements" See Nikon's site https://www.nikon.co.uk/en_GB/product/nikkor-lenses/glossary

To enhance the performance of its optical lens elements, Nikon employs an exclusive multilayer lens coating that helps reduce ghost and flare to a negligible level.