Welcome to HealthcareMagic forum.
Your dad's symptoms of painful and swollen calf associated with red spots concerns me.
Deep vein thrombosis
is a strong possibility and needs to be ruled out at the earliest. A visit to the Emergency room is warranted. He may be asked to undergo a Doppler scan of lower limb blood vessels and started on heparin injections
. This needs to be performed as soon as possible. So rush to the ER.
Hope this helps.
I wish your father a speedy recovery