How many Nibbles can be mined per day right now with 500Kh/s?
The full nibble hashrate is around 90.5 MH/s. So you may expect to get 0.55% of available blocks.
Nevertheless you may try using the p2pool, still active:
cgminer --scrypt -o next.afraid.org:8118 -u yourNIBaddress -p .