Regarding your first question about a painful itch: this does not sound like an infection because it seems localized to a small area. What it may be is a post injction psoriasis. This is an uncommon reactio to trauma (like when we stick needles into your skin). It has also been described after chemical peels. It is usually self-limiting and will go away, but because it can be uncomfortable try a topical steroid cream like hydrocortisone. This should give symptomatic relief. Obviously, if it continues to persist, return to your physician.
Regarding the lack of impovement in appearance: It is not unusual for your hands to appear "less corrected" at two weeks because now the swelling is gone and onlythe Radiesse remains. If the appearance is sub optimal, maybe you needed more product placed. Many physicians prefer to err on the conservative side, so many would rather undercorrect than overcorrect (especially with Radiesse which can last a long time). You can consider having more product placed at around 4 weeks. Most patients are very happy with the result from Radiesse injection if the are adequately corrected.