"Each of the 14 digital pins on the Nano can be used as an input or output."
There are 6 analog input pins which are also digital pins, you must take those into account.
However, Note 3 under Table 32-2 of the '328P datasheet says:
"Although each I/O port can source more than the test conditions (20mA at VCC = 5V, 10mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed:
3.1. The sum of all IOH, for ports C0 - C5, D0- D4, ADC7, RESET should not exceed 100mA.
3.2. The sum of all IOH, for ports B0 - B5, D5 - D7, ADC6, XTAL1, XTAL2 should not exceed 100mA.
(but ADC6 and ADC7 are analog input only, and should not be sourcing current)
So I would suggest that to keep your Nano healthy, 200mA x 5V = 1W be considered for the IO, and then the amounts noted above for the Power LED, L LED (which is driven by D13), and internal running of the chip be taken into account.