Remove punctuation from references to task counter

Welcome to TeX.SE! Here is a crazy sounding X-mas proposal that makes use of the fact that in LaTeX definitions are local.

\documentclass{article}

\usepackage{tasks}
\newcommand{\mydot}{}
\begin{document}
Task \ref{keytask} is more important.
\begin{tasks}[counter-format={tsk[1]\mydot},label-format=\bfseries\renewcommand{\mydot}{.}](2)
    \task First task
    \task\label{keytask} Second task
\end{tasks}
\end{document}

With an up to date version of tasks you can separate the numbering form the formatting. This makes it very easy:

\documentclass{article}

\usepackage{tasks}[2020-01-11]% use version 1.1a or later
\newcommand*\tasklabelfmt[1]{\textbf{#1.}}

\settasks{
  label = \arabic* ,
  label-format = \tasklabelfmt
}

\begin{document}

Task~\ref{keytask} is more important.
\begin{tasks}(2)
  \task First task
  \task\label{keytask} Second task
\end{tasks}

\end{document}