Is it possible for a toddler to develop an ear infection without having had a cold first? He is up screaming at night but acts normal during the day.

Be seen, eventually. Children can develop ear infections. However, you do not mention any fever or other symptoms. I would suggest he get tylenol (acetaminophen) or Motrin for a day or two, and if not improving, have him see his physician.
Night terror. It seems like your toddler is experiencing nightmares or night terrors. An ear infection seems unlikely if he acts normally during the day.