It could be just the elastic is strong in the sock and they are tight. Sometimes it’s evidence of some fluid retention…which can in early stage not be real visible to untrained eyes. One thing to look for is to take your finger and press along inner side of shin bone in various spots…if it leaves an indentation that lingers after pulling your finger away…it means there’s some fluid. There are many causes such as heart / valve trouble, venous problems…and even high blood pressure meds.
Your doctor is the one to check with. Best wishes.