Just keep up with your water changes daily and you will get through this. Basically adding as many fish as you did seems to have slighly overloaded your filter. If you filter was already cycled it should be over in a couple of days. Yuor nitrites seem to be the only thing elevated.
When you changed filters, did you add the previous media into the new one? If not, you are at the beginning of a brand new fish-in cycle. If you did, then its more than likely a small mini-cycle cause by the addition of new fish. Keep us posted. We will get you through this (we have ALL been there, I guarantee it)