It'll be fine. Don't mix it in because it might get hot. I used to put a layer of coffee grounds on top of my bin periodically. I never had any problems with it.

Mariann

Ive never seen my worms inside piles of grounds, but theyll be near the filter sometimes. Not a big deal, afaik.

I do not know how big your bin is. I have added a coffee pot's worth of grounds, at one time, to each of my indoor bins and it is fine. No heat problems. I have put big amounts from Starbucks to my in-ground bins. I do not check heat in these bins. One time I put it in a big lump and it stayed there for a very long time. I would probably take out some of the grounds in your bin and take it to your compost pile, spreading out the wealth.