Nudges have been known to trigger behavior change for individuals in different contexts. In this study, we focus on designing nudges in the context of self-directed learning (SDL) of university students and aim to identify challenges and difficulties they faced while using an online learning platform during a semester-long undergraduate reading based elective course. We describe how multiple challenges can be identified from the data logged in the learning platform. We focused on 4 of the identified challenges and designed useful nudges based on existing literature to support learners to overcome these challenges. We further examined the perceived usefulness of these nudges with a questionnaire We found that students perceive nudges which help them plan how to complete their assignments as most useful. We also found that when students propose nudges, they mostly propose social nudges and reinforce nudges. We discuss the need of nudges to support SDL and provide a basis for future design and development of nudges in self-directed learning contexts.