You can tattoo anywhere that is skin, but it doesn’t stay nice for long on the palmar side of the hand, I imagine it would be much worse on the finger tips.

I know a number of people who got their wedding “rings” tattooed on and were told by the artist that the under side would smudge and fade within a year or so. Years in, some have disappeared on that side and some are just an inky smear at this point.