Just discovered purple pea size lump near anal opening during diaper change of my 2 yr old son. No pain. Could it be hemorrhoids this young?

Surprisingly, yes. Primary care pediatricians often consult a pediatric gastroenterologist for confirmation of this.
Possible. You should have his doctor check to confirm the diagnosis and advise you as to treatment. The most common cause for hemorrhoids in children is constipation, but there are other possible diagnoses and underlying conditions, so please have your son examined.