Welcome to Healthcaremagic.
From your query i understood that your father is suffering from injury
in amputated limb.
Most probably the swelling in amputated limb is due to edema.
Edema is a collection of fluid in the tissue.
Please ask him to follow these.
If wear prosthesis
, ask him to do not wear that until swelling subsides.
Take bed rest
with elevated affected limb for some days, till swelling decreases.
Ice the injured area for the first 72 hours, 20 minutes out of every hour.
If the swelling and pain do not decrease even after this kindly take x ray
of the amputated limb and consult a nearby orthopedician.
Hope this helps.