Hello and welcome to HCM
There is no harm in wearing socks while sleeping.
However, please ensure that the socks are not very tight (the elastic part) as very tight socks can interfere with the circulation for 7-8 hours during sleep.
Regarding the pain in your foot, please get a X-ray of the foot AP and lateral view.
Since, you are a marathon runner I an suspecting a March fracture
This is a fracture of the bone(s) of the foot. This fracture is common in runners.
Second thing that I suspect is already compromised circulation. This type of pain is calleds intermittent claudication
. For this I would like to know your age and your smoking
Because the severe pain
that you are complaining cannot be just due to wearing socks at night.
Thanks and take care
Dr Shailja P Wahal