Take it off, like others recommended, clean it with a mild soap and reapply A&D in a thin layer, like you would with normal lotion. If you keep using A&D, only use it for 3-4 days, then switch to a light, scent free and dye free lotion like lubriderm for the rest of the healing process. You can leave it uncovered to sleep, covering it can leave the tattoo open to you sweating in that spot, or trapping bacteria in there (ointment doesn't last forever) and you will not hurt the tattoo if you sleep on it. Even if you see ink 'leaking' out, its normal.
My artist wraps my work with saran wrap, but they recommend no more than 4 hours to avoid sweating and causing spots that could need a touch up later.
Anyways, I'm hoping your artist gave you aftercare instructions as well, theirs makes sense first, but don't keep it covered if you don't have to.