Why does my Hamster licks my hand?

I have a hamster named Doodle... it is a name which first came to my mind when i first got him...he is an active one and we had many fun times...i sometimes let it bite my finger on purpose and he does not really bite...Doodle only so call nibble it and it does not hurt abit....but over the last few months,he stopped biting and instead,he started licking it! Why is Doodle doin it? Im just curious...everytime i greet him by puting my finger in front of him to let him bite,he licks it now adays...