Lovely work, Lupus. If you have some of the same wood left over and the split is relatively wide, you could try to make a very fine sliver and fit it in the split, glueing it with superglue. Otherwise superglue should fill the split as it's a very thin glue it gets in the smallest gap.
If you already have treated it you may have to try to sand inside the split with afine sand paper, wet&dry etc to clean it a bit.