How long does it take to heal sensitivity to ears after a night of loud noise?

Depends on damage. If the ears were exposed to too much loud noise then the sensititivty/ringing may be permanent. However, i would recommend using ear protection /plugs whenever around loud noises and avoiding caffeine and alcohol. If damage not very much you may find that over several weeks or less the damage may decrease or go away entirely. Also noise masking at night helps if it causes problems with sleep.