Have you checked your ignition switch and starter relay. It must have been some problem there. OR you might have chipped off a tooth on the starter gear. Now, in order to chip off the tooth, you can crank the engine at the time when its running.
Other problem could be of your battery. How old it is? When was the last time you changed it. Check the battery. I don't see any other problem except starter or battery.
Other problem could be of your battery. How old it is? When was the last time you changed it. Check the battery. I don't see any other problem except starter or battery.