It sounds like a beautiful idea for a tattoo.
I have a tattoo on my wrist; it's easily covered by my watch.
I'm a tattoo gal; I have 7 of them (all hidden). I don't regret any of them. But I put a LOT of thought into them, and spent months, even years, thinking them into existence.
As long as you put thought into it, its permanency and how it can be covered ... I say go for it. But I would wait for the brunt of the grieving to slow down.
I'm sorry for your loss (((hugs))).