It is OK to go ahead and add the baking soda. Also, keep an eye on your chlorine level. Until your cya dissolves in a week or so, you'll find that you'll probably need to test the chlorine level morning and evening and each time, add enough bleach to raise your chlorine level back up to 5. After the cya has enough time to dissolve, you'll be able to just test and dose it with bleach in the evenings only.

Remember, you don't want too much cya in there. So, don't retest for it, add more or backwash for a week to make sure it gets dissolved.