If you made a mistake on your 2015 return, you can file an amended return, called a 1040X, to correct your mistake. A 1040X must be printed and mailed. It cannot be e-filed. It will take the IRS 2-4 months to process your amended return.
https://ttlc.intuit.com/questions/2952222-how-do-i-amend-the-2015-taxes-i-filed-with-turbotax-online
Wait about 3 weeks and you can check the status of your amended return:
https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1