What is the ruling regarding ablution for a person who performed tayammum due to illness, and was later able to wash his hands?

If a patient suffering from a common cold fears that washing all the parts of ablution (wudu') will worsen their illness or delay their recovery, and this fear is real and not merely an illusion, then according to some scholars, it is permissible for them to perform tayammum (dry ablution). It is permissible for them to follow this opinion, especially if they are prone to obsessive doubts.