Discipline for a two year old?

My daughter this morning was being silly and hit my foot with one of her toys, she showed concern when I said that it hurt, and I asked her to say sorry to mummy, but she refused, she is nearly three and understands what I am asking her to do, so she is sitting on her time out square in the kitchen until she says sorry, am I going too far with this? she has been misbehaving a lot since I had my second daughter, and I really dont want to have an uncontrollable and child. I'm not angry at her for hurting my foot, i'm not actually angry at all, I just want to push the point that if she hurts someone she must say sorry, any advice or help?