Indeed that’s an out of memory error. If you have the disk space to add swap, that will be enough, although the process will take more time than if you were to add RAM. Your hosting provider might offer the chance to upgrade RAM temporarily and then revert, which will probably cost you a couple of reboots, a little down time, and a few cents of extra cost.
Edit: to be clear, memory = RAM + swap. RAM is fast and swap is cheap.