Do you mean 2000 IUs? I presume so, and I presume you were given D3, since for a vitamin D deficiency that's the preferred choice.
You shouldn't experience any problems with vitamin D itself at 2000 IUs per day. But you could react to one of the other ingredients that comprise the pill. Many pills include soy, milk, or gluten among their inert ingredients, and that can be a problem for some people.