I didn't pay EMI for the past 1 year.
This has already impacted your credit score. Not paying dues will be shown as delinquent in your report and something not paid for a year has already resulted in lower credit score.
If I pay the One time settlement , how it reflect in CIBIL score?
This will reflect negatively in your CIBIL score. The specific loan account will show "Settled". Although it may show zero as dues. This will continue in the report for 7 years. Generally Banks may avoid giving new loans to such customers. Also note if you are going for it, have a clear statement from Bank that the account is settled in full. More often, the agencies working on behalf of bank may tell you its "One time Settlement" but they record this as part payment and keep chasing you for more payments.
I am planning to pay regular EMI after 1 year and settle for full.
This may be a slightly better option. Generally any delayed payments show up as Days past Due in monthly buckets going for 2 years. These then drop off. So if you start repayment in another one year, it would be 2 more years before your score comes back to normal. So total 3 years compared to 7 years on One Time Settlement.
If you plan to go down this route, check if the Bank can give you a payment holiday. Essentially it means the repayment schedule is redrawn and you start payment after one year. This means that it will not show up as Days past Due.