white gum which has developed in the area which is painful is either due to gum infection or due to decayed tooth which is infected. when the tooth gets infected and develops pus, it comes out of  gums thru intraoral sinus which is white pimple like growth on the gums. This can also be due to some gum infection. In either of the case you have to visit your dentist and get the treatment done after getting the proper diagnosis. If it is due to infected gum then deep curatage and scaling will serve the purpose but if it is due to infected tooth then Root Canal Treatment has to be done. For more info on RCT you can read this article... http://www.identalhub.com/article_why-is-root-canal-treatment-rct-required-299.aspx