Thank you for your query.
I can understand your dilemma. I would have loved to be of help to you but cannot give a definite comment till I see the lesion. If the lump is not increasing in size nor giving rise to pain then I shall suggest that you wait and watch. If either of the two things are occurring then it shall be advisable to seek the opinion of either a dermatologist
or a surgeon.
I hope I have answered your query to your satisfaction.
Wishing your son all the best.