I have agreed to work for company for next two years after increment. Can I Resign after one year?

Hi, I started my career in a company in 2018 and have been employed in that company since then. In January 2020 I got a pay increment as I wanted to leave the company for low pay for another company. But the current company gave me a counter offer which was 5% less to the company to which I applied earlier. I took their counteroffer and they asked me in the next appraisal cycle that is in January 2022 we will increase the 5% based upon your performance. Then the company asked me to work for them for the next 2 years and I agreed through mail as the office was closed due to Corona Virus. I didn't give my consent on paper or there is no written agreement for the same. Now I really want to leave the company as I have completed 3 years here. Now the Director is refusing to give permission to leave the company and is saying you have agreed to work with us for 2 years. He said you can't leave the organization and you have to work for us for the next 1 year. What should I do as I have a good career opportunity with other company and I don't want to miss this opportunity.