This might be Amateur in Chancery by George. O. Smith. Google has a preview available.
If so, you've got some of the details confused, but I could still recognize the story from your description. From the preview plus my own (imperfect) recollection of the story line:
a space ship that crashed on either mercury or Venus and injured the pilot
It wasn't a spaceship per se, but an experimental matter transmission device.
It was transmitted, with a pilot on board, from Earth to Venus as a trial run.
The ship itself was unharmed, but the pilot was unconscious and dying, after mistakenly believing that the atmosphere was safe and opening the airlock.
The alien will do something that will save the pilot, but he needs to understand left from right.
The only way for the ship to be returned to Earth was for the correct button on the control panel to be pushed. If the wrong button was pushed, the ship would be destroyed, killing anybody on board.
The Venusian was able to communicate with the team on Earth, I think via telepathy, but without a common reference for left or right there was no obvious way to explain which button was which. (I think they were different colours, but the Venusian wasn't able to distinguish them.)
Earth had to teach the alien left from right so it could do something to the pilots heart
- I don't remember this part of the plot well, but from discussion elsewhere I believe that the pilot's heart was involved, though not in quite the way you describe.
Credit: Gwydion Madawc Williams, on Quora.