When an ant bites you, it injects some saliva which contains chemicals which your body may react to. The most common reaction would be redness and swelling, as well as itching. In some people, who are more sensitive to these chemicals, this swelling and redness may be quite pronounced, as it sounds like it is in your case. If the swelling is significant, there may even be some bruising or breakdown of small blood vessels in the area of the bite, which could lead to the dark red, speckled appearance that the bite currently has in your case.
I would suggest that you go see your primary care doctor
about this issue for a couple of reasons. First, it is important to make sure that the bite is healing appropriately. Any insect bite does have the potential to become infected, and your doctor can rule this out.
Secondly, it is important, given the significance of the swelling you experience, to make sure that you do not have an allergic reaction to ant bites. If left own their own, allergic reactions to insect bites can be very serious, even leading a life threatening reaction called anaphylaxis, which involves trouble breathing. Your doctor will be able to evaluate you for a serious allergy to ant bites.