Mothballs protect things put away for a long time, so they stand for plans or feelings shelved and kept for later. Their sharp smell is traditionally linked to the past and old wardrobes.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.