Update that may help anyone else in the same situation:
Deleting the .lck on its own and restarting fusion did not work on it's own.
I fixed this issue as follows:
1. Uninstall fusion
2. IMPORTANT STEP - followed these instructions to remove all traces of fusion from mac: https://kb.vmware.com/s/article/1017838
3. Went into vm machine bundle and deleted the .lck folder
4. Reinstalled Fusion
5. Manually opened the vm by double clicking on it, which then automatically opened fusion and the vm started as usual.
Phew.