well...I am not an expert, but what I learned here, has just brought me through a fishless cycle !
Others can correct me if I send you on the wrong track
I reckon you are probably better not doing a water change, just keep waiting.
If you see the ammonia level dropping, add some more to keep it around 4ppm, and keep waiting.
2 or 3 (or 4) weeks in you will see the nitrIte rise a bit, and over the next few days, it should drop to 0ppm.
AFAIK you should keep adding ammonia every time you see the level drop, until you come to a point where...
24 hours after adding ammonia you see ammonia back to zero,
and nitrIte back to zero. NitrAtes will have risen by this stage to approx 40-80ppm, so you need to do a 50% water change to bring it to 20ppm or less....and then you can add fish !
If you see Amm, and Nitrites at zero on say Monday, and you aren't able to get to the fish shop until for example Saturday, then you need to keep adding the ammonia, to feed the bacteria that has built up...until you add the fish, and then
they will supply the ammonia for the filter bacteria.
I just came through my first fishless cycle, and it took mine three and a half weeks, but apparently every tank/filter combo is different, and it might take less, or it might take more time.
Well worth it though