It shouldn't be an issue, but personally, I'd get some thin superglue/CA and run it into the crack. I'd do any staining first, as any excess glue will stop the stain from penetrating, but CA dries clear, so if you are just TruOiling, then you won't see the CA underneath. Mask off the surrounding area as much as possible to avoid too much excess, as thin CA is very runny indeed.

Medium thickness (standard) CA is unlikely to wick into the gap. You may need two or three applications to fill the gap.