What comes after you have programmed a Bluetooth Low Energy chip with Nordic SDK and are ready for deployment?
Development board to custom hardware:

Development Boards (dev-boards) are incredibly useful for quick prototyping. Typically, after validating your initial design using a development board, you would move to designing a custom PCB suited for your application. Software development can then continue using your application-specific hardware.

Possible reasons to design a custom PCB:


The product needs to fit in a specific enclosure.
Smaller PCB = lower cost PCB in mass production (development boards can be large relative to your product).
Not all components on a development board are required in a mass-produced product. Reducing part-count lowers your cost.


The list goes on. All of these points fall under the princicple of Design For Manufacture (DFM).

Programming your custom hardware in the factory:

You may be able to include a programming connector on-board. This can be any connector that interfaces your hardware to a programmer (such as a Segger J-Link).

There are a few reasons not to use a connector to program mass-produced products:


It is often not desirable to require an operator on a factory line to plug in every single board to the programmer manually. This takes operator time, which is valuable.
Adding a connector onto your product for one-time programming incurs unnecessary cost.
Connectors consume space on the PCB, which (depending on your product size) you may not have.


One very common solution to this is to use a "bed of nails" fixture. This involves pads on the bottom of your PCB that line up with spring contacts on a programming fixture. Not only can this be used to program your finished PCB, but can also make test-points available for automated checking on the factory line.