Validation in Slide Outs (desktop)

I have slide out with a bunch of filters.(sorry, because of private info I can't publish them) I can apply 1, 2 or 5 filters by clicking "Apply Filters".

By clicking on filter I can get to its settings (another slide out). To apply changes I should back and to click "Apply Filters". Changed filters have indication that show user that they are ready to apply. Cause of technical restrictions I can't put "Apply button" right on specific filter slide out.

The question is should I allow user back to filters and disable "Apply Filters" button and additionally to show red indicator etc? Or should i disable yellow navigation bar "Filter List" (img 2) and don't allow user to back? so, when he open filters slide-out again he see this invalid filter slide out, not all list of filters (img 1)