Dua for the sickness

اللَّهُمَّ ربَّ النَّاسِ ، أَذْهِب الْبَأسَ ، واشْفِ ، أَنْتَ الشَّافي لا شِفَاءَ إِلاَّ شِفَاؤُكَ ، شِفاءً لا يُغَادِرُ سقَماً

“Allaahumma Rabban-naas, adhhibil-ba’s, washfi antash-Shaafi laa shifaa’a illaa shifaa’uka shifaa’an laa yughaadiru saqaman”

“O Allaah, Lord of mankind, do away with my suffering. Heal (me) as You are the only Healer and there is no cure except that of Yours, it is that which leaves no ailment behind”

(Al Bukhari (with Al-Fath 10/206) and Muslim 4/1721)