just for your own peace of mind I would pop him along to the vets. Dont judge yourself, we all have accidents, and you obviously wouldnt have done it on purpose. My son got himself in the tumble dryer when he was small, he pulled the door shut, and fortunately it was turned off at the mains, otherwise he would have been going round in it before I found out. At least now you will check all your appliances before turning on, or make sure you know where kitten is, to make sure it hasnt got anywhere it shouldnt!