You had a long discussion with yourself about this wherein you decided that the side of you who thinks in images should come up with ideas and the side of you who thinks in words should criticise them.
The only thing you could think of was to wait until the box (probably) opens in two billion years. It might not even open, you have no idea what it's going to do.
You thought about using time travel to skip to the end but you don't have any time travel abilities or technology and you're stuck on this world until you break the self-inflicted curse by either dying to Hearts or killing Hearts. (probably the former, preferably the latter) So you formed a plan: Put the box down, fight Hearts as soon as possible, die, hopefully respawn near a thyme traveller, get him to send you 2bn years into the future, see what happens with the box. IT IS FOOLPROOF.
Current objective: Find out where Hearts is.
Optional objective: Find some way to defeat the vastly stronger Hearts that doesn't involve the box.