My 13yr old son woke up yesterday to a swollen and itchy penis. what could this be. he is not sexually active?

Balanitis: If not circumcised could be a posthitis or Balanitis. Bubble baths, soaps could cause this. Is he masturbating?

Bug bites: I find the more common cause of this is bug bites.In my local this is often chiggers, but other bugs can also do it.An occasional case of poison ivy also presents this way.Local application of a weak steroid cream can reduce the itching and the process fades in a few days. Poor hygeine/masterbation are less common.