Well, introductions went too fast. That's what happened. Playing sesions are closer to the last stages.
It would be wise to separate them again, and start a slow introduction. It could be something like this:
First week, kitten confined in a room, lots of treats and playing with your cat. Feed him outside the kitten's room.
Week two, put a mesh or something similar on the door so the cats can see each other but can't actually touch. Expect some hissing and growling. Continue feeding them each one in its side.
Swap them (cat inside kitten's room, kitten in another room, not the entire house yet if the kitten is too small or too scared) so they can smell each other's "belongings". If cat decides to use kitten's litter box, just let her (it is her way to say I'm the boss here. Scoop right away.)
See how all that goes, and eventually you can reunite them again. Anyway I wouldn't let them alone in the house together for two or three more weeks, just in case.
Introducing two cats -- you can search that sentence here in the forum or just google it, you'll find a lotta info.