Is a terrible thing to face.
Wishing you courage & peace in rough moments.
As to ring on left hand--
death forced an ending. Sorry.
However, no rules exist. If want to wear ring there, do it.
For as long as you want.
There are companies which create gemstones from cremation ashes.
For jewelry. Including rings.
This may suit your wishes, as each gem is unique. And a connection.
example(found through google search):
https://www.cremationsolutions.com/...ystals-made-from-the-ashes-of-people-and-pets
Another option may be to refashion husband's ring into new piece.
To wear on your left hand.
Or add it unaltered to your necklace chain.
No rush. Take your time deciding.
Remember, no rules. Just yours.