A knothole is a small opening where a branch once grew, so it is read as a glimpse into something hidden or a place where secrets are kept. It can also stand for an old wound that has healed over.
When this appeared in your dream, what were you feeling?
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.