If you’re wondering whether or not no follow links can hurt your SEO, the answer would generally be no.  This isn’t the case 100% of the time.  There are some instances, if not rare instances, where rankings could be jeopardized.  As an example, if you left a ton of no follow comment links of different blogs, this could be one of the exceptions to the rule.  Google can take a course of action to manually take spam action on your website since you left spam links.

In this is the case, Google has said that they generally just drop no follow links out of their link graph.