@Angie
This is likely to be oedema / edema, which does need to be looked at by a professional ASAP I feel.
From the official Dutch approved by professional doctors and Dutch health care website:
https://www.thuisarts.nl/dikke-enkels-of-onderbenen
I'll translate for you:
Your ankles or lower legs could become swollen by fluid accumulation
This is caused by veins which are not working properly, fluids will then leak out.
You'll get pressure bandage (from the doctor) and you'll need to walk a lot.
This way your muscles in your calves will cause a better blood flow to the heart.
When your leg is no swollen/thick, you could start wearing elastic support stockings.
There's no specific medication to let your veins work better.
Uw enkels of onderbenen kunnen dik worden door vocht.
Dat komt door aderen die slecht werken, er lekt dan vocht uit.
U krijgt drukverband om uw onderbeen en moet veel gaan lopen.
Zo drukken de spieren in uw kuiten het bloed beter terug naar uw hart.
Als uw been niet meer dik is, kunt u elastische steunkousen gaan dragen.
Er zijn geen medicijnen om uw aderen beter te laten werken.