Even though you changed the oil before it is best to change it again. If there is any fuel in it that has been sitting it is most likely bad and could clog your fuel lines or injectors, if applicable, making it difficult or impossible to start. So it would be wise to flush the old gas and replace it with new gas. It would be a good idea to check the spark plug for build up and replace if needed. Once this is done try and start it. If it doesn't start and you didn't have any previous problems then your fuel line are most likely clogged or your pump has seized. If that happens you can get it tested at most auto parts stores i.e. Autozone or Andvanced. If tested bad you will need to replace it. Once you get the bike started let it run for at least 5 minutes. Check for any leaks while it's running and periodically over the next few days. If there are any leaks your gaskets are bad and will need replaced. As long as this is done and the oil is done to the proper specs there will be no damage.