Most people find little children's speech rather cute, and really enjoy listening to toddlers talking. While your two year olds mispronunciation is nothing to worry about, it is a good idea to encourage the correct way to say the words, by looking at books together with lots of pictures in them, and get them to point at the pictures and name the objects.
Another way is to have plenty of face to face chats with your toddler, so that he or she can see you as you talk and use you as a model when he or she tries to say the words themselves.
Correcting your child when he mispronounces a word can damage his self confidence. It is far better to just let him get along with it at his own pace – the words will eventually come out right!