Sour asscheeks is a term meaning someone is grumpy and grouchy.
Sometimes when they have lemon juice in there asshole or on there ass cheeks causing irritation!
Jessica: IM GONNA SHOVE U UP MY VAGINA AND PULL YOU OUT MY NOSE ASSHOLE!!!
Matt: I poured lemon juice on her asshole!
Jon: She sure does have some sour asscheeks!