Its been 3 weeks post tace for stage4 hcc for my father. Fever is not getting subsided even now. I'm worried, please comment, is it normal?

Fever from TACE. After chemoembolization it is common to have post embo syndrome which includes fever. This far out, fever is unusual and would make most providers concerned about hepatic abscess. Labs and repeat imaging should be performed. Contact the provider who did the embolization or call your oncologist.
Better call. The interventional radiologist that did the procedure. May be forming a liver abscess or biliary obstruction with associated infection. Please call soon. The infection can spread to the bloodstream which is called sepsis. Sepsis can be very dangerous.
TACE. Not sure what hcc means (hepatocellular carcinoma?), but when transcatheter arterial chemoembolization is used the infarcted areas of tissue may release cytokines which induce fever. Three weeks sounds like a lengthy time however and might worry about secondary infection. Hope he feels better soon. Good luck.