Do a water change if you have high nitrite. Don't worry about nitrates first. If you have moss in there, they will do the work for you. (I heard moss love high nitrate) I am in the same circumstance. I still have ammonia and still have nitrite and still have nitrate. I just keep doing water change when I see them high and they are coming down
Really want to get my shrimp in there sooner or later. I do use the Tank cycle liquid. It helps!