Infection inside the RCT tooth develops due to nerve segement left inside while the tooth is capped. Now talking of the white spot, it can be a dentin layer that is acting as a demarcation between underlying nerve and filling. Now if the tooth is hurting than its most probably due to the fact the filling is acting as a conducted to transmit pain.
You can wait for the self healing process but if the tooth is hurting than you can go for re RCT. Also sometimes white color can be seen due to constiction of blood vessels in the area or it can be due to plaque in the gums...For more info on gum surgery you can visit the link...http://www.identalhub.com/article_what-is-gum-disease-surgery-339.aspx