Aisha, may Allah be pleased with her, said: I asked the Messenger of Allah: ‘O Messenger of Allah, if I know what night is the night of Qadr, what should I say during it?’ 

He (The Prophet PBUH) said: ‘Say: 

Allahumma innaka `afuwwun tuhibbul `afwa fa`fu `annee

O Allah, You are pardoning and You love to pardon, so pardon me.’ “

(Ahmad, Ibn Majah, and Tirmidhi).

Please try to read this dua (supplication) abundantly during the last 10 days of Ramadaan, especially on the odd nights.