Hello and welcome to e health forum.
You seem to be having idiopathic edema.
Idiopathic edema is a syndrome of real or perceived fluid retention with swelling of the lower extremities.
Such edema can present after a exhaustive travel or stress related activity, specially in elderly individuals. Fluid distribution in the body is influenced by gravity so that after a period of resting, the fluid collects in the dependent parts of the body.
The severity of fluid retention varies from time to time. You may find relief by wearing a crepe bandage or a hose type medical stockings to reduce the swelling. In addition keeping the limb elevated while sleeping or while at rest is important.
You might consult a doctor who can examine you and rule out other causes of edema, including renal and cardiogenic causes and if needed initiate necessary treatment for it.
I hope this helps.