I would look at some other factors besides that small separation to make the decision to recut and callus. Here are the questions I would ask: How is the overall condition of the cutting? What variety is it? How successful have you been in rooting others in the same environment? Do you have a heat mat? etc.

Based on that picture and it being late spring and warm outside I would take my chances and root it. Good luck with it.

I rooted a bunch that looked like that, they all did just fine. I'd probably not risk recutting and opening it back up.