One of the quests was to complete a Nature aspiration goal. So if your sim doesn't have the Nature aspiration I am assuming you must change your sim's Aspiration to complete that goal? Not sure exactly how I go about doing that but is there a potion you have to drink (or your sim has to drink) to change Aspirations under the Rewards store?
When you open the aspiration panel, click on the star icon that is on the top right hand side. Then that will open the section where you can choose a new aspiration. For the event task, choose an aspiration from the Nature section, then confirm your selection. Your sim will then be able to do the new aspiration.
I changed my aspiration to the collector goals and was going to go digging, but I did something on my lot and it checked off for me. So, it seems you don't need to change your aspiration - the game uses some sort of fairy magic to find it and check it off for you. 😁
I wish that fairy magic would work universally. I can't tell you how many times I forget to change to the friend aspiration when greeting others or I don't catch it quick enough to change to the comedy one when my sim autonomously tells a joke.
