Yellow key in forest for tonic?

[Sawtaytoes]

There's a cage with a tonic wanting a yellow key, but there's not one around. I'm at the place where I have the desert unlocked.

Without any spoilers, is it possible for me to open that cage now or am I supposed to wait until later?

[Jether[cn]]

jump and left button(lb on controller)

[Nibbie]

Most likely, you haven't explored enough. If you are talking about where I think you are, explore to the south of the tonic more?

[Sawtaytoes]

@Jether[cn] was correct. Left-Button did it!