Thank you for your query.
The problem that you describe is not autism
. However with the high pain threshold your son must be hurting himself which is giving rise to the reactionary conditions. I suggest that you show the bumps to your doctor who will examine them and guide you accordingly.
In case your son has autism then the doctor shall give you a proper guidance or arrange for further evaluation.
I hope I have answered your query to your satisfaction.
Wishing your son an early recovery.