Welcome to the club. Nearly every Nissan Primera/Infiniti G20/Nissan Sentra will have this problem at some time or other. Lucky for us it is simple to fix. It is, however, completely unrelated to the check engine light. It is also completely unrelated to the intermittent lights on your blower switches. As I understand it, the contacts on these lights are small and get dirty over time. Don't worry too much about it.
Go to your local Nissan or Infiniti dealer - Nissan might be cheaper - and ask for a new Blower Motor Resistor. It will cost under $30, most likely under $20.
For further instructions, go to
SE-R.net
Good luck,
Emily