My 5 (FIVE!!) year old is still in diapers at night, because he hates the feeling of the stretchy elastic sides on pull-ups at night.
He's fully potty trained in the day, and actually prefers sleeping on a pallet alongside his brother's bed more often than his own bed.
Kids are weird, and very different from one another. Your DS is fine, OP. Don't stress out about, people that are saying to go to the doctor about this are nuts. You'd be laughed at for being concerned that a 2 year old isn't potty trained.