There is no real answer to that. I think David Gilmour once said: "Don't try to be creative to early." and i agree with that but i find it a bit harsh and to general. If by "your own song" you mean messing around with a view chords then go ahead, just be realistic about your skill level and don't get depressed if the result don't match the idea.
Learning to play is a lot like learning a language. As a beginner you only know a view words, this may be enough to say hello, but you will have a hard time if you want to expressing yourself. As you learn and progress you will find it easier to express your feelings and thoughts, and just as with the language you should give yourself a view years time! There is no need to hurry, and it's worth every second you put into it! It's a ability that will stick with you for the rest of your life.
http://www.youtube.com/watch?v=EIahlvUu8Nw
Cheesy video - but that's actually poetry.