I have hired a Freelancer SEO last Year & He build mostly no-follow backlinks for my site. Will it effect my website SEO ranking? Also Should we totally avoid No-follow backlinks OR not?
No Follow backlinks most often do not have an affect on your sites rankings. If you have a no follow link in within a blog post, this can be good as it can drive traffic to your site. But if all you have are no follow profile links, than they are almost useless, unless it is to counteract the amount of Do follow links to your site.
Just to say that it's not normal and NATURAL to Google if you have 1,000 dofollow backlinks and only 2-3 nofollow backlinks. That's why nofollow backlinks are being used to make everything look normal to Google and other SE's.. And yes, they are good for traffic too!
Just focus on building links naturally - follow or nofollow does not matter. This way you will have a healthy ratio of follow/nofollow links. As for your question, it does not help in passing link juice. But it does help in Google discovering your webpage and thus improves crawlability of your website.
Both kinds of links are necessary for SEO. Both can be followed by real people, Nofollow attribute is for search robots only.