If you have nitrites, the tank is not completely cycled. In a cold water tank, it can take up to 8 weeks to get past the nitrite phase. <That was how long mine took!>
If you've done a fishless cycle, then added the fish just a couple weeks ago, this would indicate that bacteria colony is not big enough to support the bioload (& goldfish are messy!). The bacteria will catchup in a week or 2. <This is what people call mini-cycle.>
You would want to maintain nitrites at 0.25 or less. That would mean water changes for the next little while.
You actually don't need a lot of salt to protect against nitrite poisoning (Cl
- level 20x that of nitrite is needed.) 1/2 tsp/gal
is around 0.07% & is perfectly adequate.