According to Madhhab:
If a person observing the Sunnat-e-Mukkada I’tikaaf during the last ten days of Ramadaan had to nullify his I’tikaaf after three days. Is Qa’dha required?
It will be best to make Qa’dha of the complete ten days I’tikaaf after the month of Ramadaan which should be accompanied with the ten fasts. However, this command is not obligatory. A person may suffice by making Qa’dha of the day the I’tikaaf was nullified.