If you are already in Bali, you do not need a COVID test to go to Nusa Penida or Nusa Lembongan. As these islands are part of the Bali province, a valid rapid or PCR test is not required to travel to these islands.
You can hop on a fast boat from Padang Bai or Sanur and enjoy the islands to their maximum. The most famous spots are usually over crowded at this time of the year… But now, you can explore with very little people around you and take stunning pictures.
Of course, wear a mask as it is still mandatory and respect the protocols put in place in the areas you visit.