Flooring Tile - Botched tile job, or fixable???

i just laid a 4X4-foot section of 8X8-inch tiles in my entry 4 days ago (haven't even sealed it yet), and one of the tiles seems to be moving ever so slightly when stepped on and the grout on one side of it has a crack. am i correct in thinking that i need to remove that one tile, and whatever "thing" is under it making it wobble, reset it & regrout around it? if so, will the new grout be indistinguishable from the 4-day-old grout? or will it be an obvious "fix"?

and was i supposed to keep plastic over it or mist it with water after i grouted it, to keep it from drying out too quickly? the grout instructions said "periodically mist with water for 3 days" but i didn't know how often that meant, so i only did it once a day....not enough???

have i failed miserably?????

Just replace the one tile and it'll be ok. No to the plastic.

Thanks! sorry to bug you again, but what about the misting? is that really necessary and exactly how often should i do it & how wet should i get it? the instructions said "periodically for 3 days". pretty vague........

thanks!!!

skip the misting too.