this is almost certainly not your child lock, as that only prevents the door being opened from the inside. i would suggest that the problem is either the central locking unit on that particular door or the rod/cable that connects from the c/l unit to the door handle has worked loose, or lastly there is a problem with the rods/cables inside the door panel that controllocking unlocking of the inner door handle. a local garage should be able to gain access with a bit of patience, for a small fee. i would suggest you let them do the rest of the work while they have the door open unless you are experienced with auto electrics/mechanics.
jayjaymotorsport
March 2008