Since there is no formal contract entered into with the organization, i.e., as you were not given an appointment letter in which the terms and conditions of employment are stated, there is no legal binding on you to serve the minimum notice period to quit the organization, which is generally a 3-month notice period.
Secondly, the organization in which you served for one year cannot establish the relationship between you and the organization as 'Employee-Employer' in the absence of any contractual agreement, i.e., in your case, an appointment letter.
Hence, there will not be any legal complications for you with the organization, assuming that you have not signed any agreements/contracts with the company.
Regards