One of the famous Ayahs recited again and again by people for cure of illnesses and relief from hardships is Ayah 62 of Surah Naml:

“Who is it that answers the distressed when they call upon God? Who removes their suffering? Who makes you successors in the earth? Is it another God beside Allah (SWT)? Little notice you take!” The distress which has been mentioned in this Ayah is the lack of Caliph and the chosen ones in the earth and this is the real and true distress which needs to be removed, because without Divine Caliph in the earth spread of justice which is the main aim of all the prophets cannot be established; and hence, peace and security cannot be provided as mentioned in Ayahs 40-41 in Surah Hajj and Ayah 55 of Surah Noor. That is why it is said that the true distressed one is Imam Mahdi (AJ) and the real urgency for people is the establishment of government of Imam Mahdi (AJ). God Willing this will happen soon and the distress will be removed.

Source: en.shafaqna.com