The nofollow attribute is a ranking factor. If a link has this attribute attached to it, the linked-to page doesn’t receive any PageRank.

In general, Google doesn’t follow nofollow links. This means that Google doesn’t transfer PageRank or anchor text across these links. Only nofollow internal links that you don’t trust. Avoid using nofollow to manipulate how PageRank flows on your website. source

Google also recommends not to use nofollow on internal links as well: