I'm sure you've already put the chicken in the the crockpot and already had your meal.
But yes it's okay to put the frozen chicken in the crockpot without thawing first.
What I do is get whatever I am cooking up to temperature where the food is cooking and then put in the frozen chicken or other meat.
I usually do this overnight so that when I get up in the morning the food is cooked and ready to eat.
I then put the rest into the fridge and then just put the crockpot pan back in the crockpot to reheat and I'm good to go again.