After defeated the Antlion, it'll drop Sand Pearl which is a cure for Rosa's illness. Now go all the way back to Kaipo, the house where you met Rosa. Deliver the Sand Pearl to her.

Watch a cutscene and fight another scripted battle. Don't worry, you be fine.

Do not forget to pick up Item Lore augment in the village after you woke up. It spawns near a well to the north of the village between two coconut trees.