I wonder (1) what it is that they wanted to graft it and (2) that they grafted it onto Hylocereus (which makes it grow vigorously). Anyway, to your question - now is fine, if you can give it some additional bottom heat. Otherwise, waiting until spring is a good idea.

Thank you for your quick response. Maybe I will wait until spring :) and I hope top cactus going to have

It does look like an Echinocereus, so that's precisely the flower you should get on it.