Since it was not conviction as well as it will come under petty offense exception, can I get citizenship next year or wait for another 5 years for GMC

A conviction for shoplifting can bar eligibility to become a naturalized U.S. citizen (and even can have more harsh consequences). Many people are surprised to learn that the USCIS treats some cases dismissed following pre-trial diversion as a "conviction." That can be true even if the criminal court does not consider it to be a conviction. A "conviction" for immigration-related purposes can turn on whether as part of the pre-trial diversion an applicant acknowledged the material elements of the crime (such as through an allocation). This is true even if a criminal case has been dismissed and the file has been formally "sealed." There really is no substitute for you to obtain court-certified copies of the full set of disposition documents and to consult with an immigration attorney who, after learning all of the relevant information and seeing the disposition documents, could advise about eligibilities, options and strategies to attain your goals, and who then could offer legal representation in the often complex application process.