The most popular spot in Nusa Penida, and also the reason many people visit the Nusa Islands, is Kelingking Beach, also known as T-Rex Beach. I would say the views are even more beautiful in person, and it's 100% worth the visit. It's up to you to decide if you want to enjoy the views from above or climb down to the beach, but it's important to know that the path down isn't well-made, and it's an intense hike, especially if you come back up when it's midday and hot. I've seen people pass out on their way up.
Two things to know as well are that Kelingking Beach gets super crowded. If you walk down the stairs a little bit, you have the best location for pictures without going all the way down. There are also monkeys in the area, so don't feed them anything; they get aggressive.