Going by his age, chances are this is normal, as this is the age he would start to have some hormone surges. Lumps in nipple area can occur. Generally these types of lumps will go away on their own.
However it is best that he be seen, so do keep his appt, as I am to a disadvantage of not being able to see this. But do know this is normal to occur.
Best of luck to you both Hun, Hope this helps, If you need anything else please feel free to ask. If you found this helpful don't forget to click the *ACCEPT* button and leave *POSITIVE* feedback.