Sorry bro but you can't run slot-1 flashcards with FWnitro. :/
Normal games will work and slot-2 cards too.
If I were you I would try this: (It's the only way)
1. Borrow a slot-2 flashcard.
2. Put Flashme on it. (or noFlashme, see which one works)
3. Reflash your DS.
If you CAN run the slot-2 flashcard but you can't open Flashme properly (2 black screens or something, that's what I had).
Then hold SELECT + START + A + B + X + Y and boot your DS. It will start the slot-2 card in recovery mode and then you should be able to run Flashme properly.
If the booting in recovery mode doesn't work, then just try it ALOT of times untill it works.
Good luck!