I assume you mean your bathroom ceiling needs fixing. If it is drywall, do the following:
Cut out a hole that is square. Have the edge of the hole be flush with nearby studs.
Fasten 2x2 nailers on the studs.
Fasten a patch piece of drywall up to the nailers and existing studs.
Tape and finish the drywall.
Prime and paint.
Detailed instructions for a similar repair are given at
How To Repair Holes in Drywall and Cracks in Walls