\documentclass{report}
 \usepackage{xepersian}
\settextfont[Scale=1.2]{XB Niloofar}
\setdigitfont[Scale=1.2]{XB Zar}
%%===================================
\newcount\mydigits
\XeTeXinterchartokenstate=1
\newXeTeXintercharclass\mydigitscharclass
\newXeTeXintercharclass\mydotcharclass
\XeTeXcharclass `\. \mydotcharclass
\mydigits=`\0 \loop \XeTeXcharclass \mydigits \mydigitscharclass \ifnum\mydigits<`\9 \advance\mydigits by 1 \repeat
\XeTeXinterchartoks \mydigitscharclass  \mydotcharclass = {}
\XeTeXinterchartoks \mydotcharclass  \mydigitscharclass = {}
%%===================================
\begin{document}

لطفاً قضیه‌ی 1.2 را چاپ کن.
%%===================================
  \end{document}