i would try calling your dr again just to be sure but there are several possibilties:
phlebitis (inflammation in the blood vessel) of which there is no real treatment for now just warm compresses and rest
its really early for site infection but rare cases have occurred this fast
normal inflammation postop (some mild swelling but not usually hot)
very unlikely but also possible a small venous clot
the hardnes is likley just due to postop inflammation, the temperature change is what i recommmend calling your dr again for.
Please click accept if no more questions, positive feedback appreciated
bonuses always appreciated
**Always seek the advice of your physician or other qualified health care provider with any questions you might have regarding a medical condition. Never disregard professional medical advice or delay in seeking medical treatment due to information obtained here. The content of the response, such as text, graphics, images, and information posted on the site as well as information obtained through "links" on this site are for informational purposes only. This answer is to the best of my knowledge and experience and is in no way infallible**