ぬちぐすい(nuchigusui) is an Okinawan dialect, which literally means 「命の薬(inochi no kusuri)」.
ぬち=命=life
ぐすい=薬=medicine
It can mean anything that heals you in anyway. Or anything that makes you feel good and cheers you up.
Delicious food, beautiful scenery, someone's kindness, mother's love etc.