I had a lovely big kefir grain, been making kefir everyday for years. Today I accidentally put it in the blender with the milk and fruit. I managed to sieve out a few tiny bits of grain which I've put into milk. Will they grow again?
The grains are really just a symbiotic colony of microscopic yeasts and bacteria that grow in and ferment milk into kefir, similar to the "SCOBY" that ferments kombucha, or the "mother" that ferments vinegar. The individual organisms are far too small to be harmed even by the intense action of a professional blender; if you managed to rescue some, then given sufficient food (i.e. milk) they should grow and develop new grains.
The one caveat here is that the specific strains of the organism can differ, potentially even within a colony; it's possible that the grains which survived blending won't contain exactly the same mix of bacteria and yeast that you had originally, though they should be pretty close.
You should be able to resume your normal daily production and the grains will get back to their former size eventually. Just check the next few batches before consuming to make sure the kefir hasn't been thrown off.