Here's some good information about migrating/upgrading from 2010 to 2013.

Migrating/Upgrading - What you need to know

Upgrading Nintex Workflow 2010 to 2013

Thanks for your reply.

My question is that I am just migrating one site collection and as far as I know we need to migrate the entire Nintex database to continue the running workflows hence it wont be a feasible solution for me. Could you please help me in this?

Since you need to have the workflows running in their present state, I believe your only option is to move the entire Nintex content database and attach it to the new environment.  You could contact Nintex Support to see if they have any feedback.

Here's more information that might be helpful: Nintex Workflow Backup and Restore

Thanks Eric, the issue is that  SharePoint 2013 environment is already existing and has configuration database due to which we will need to migrate the Nintex content database without configuration databases