\begin{tikzpicture}[line cap=round,line join=round,x=1cm,y=1cm]
\tikzset{
        every pin/.style={fill=yellow!50!white,rectangle,rounded corners=3pt,font=\tiny},
        small dot/.style={fill=black,circle,scale=0.5},}
\begin{axis}[
        axis x line=middle,
        x=3cm,
        width=40mm,
        height=20mm,
        xmin=0.5,
        xmax=3.5,
        xtick = \empty,
        x axis line style={thick,-latex},
        xlabel style={anchor=north west},
        axis y line=none,
        anchor=left of origin,
xlabel=$x$,
extra x ticks={1, 2, 3},
extra x tick labels={$x_0 - C$, $x_0$, $x_0+C$},
]
\draw [line width=2] (axis cs: 1,0) -- (axis cs: 3,0);
\addplot[only marks, fill=white, thick] coordinates {(1,0)};
\addplot[only marks, fill=white, thick] coordinates {(2,0)};
\addplot[only marks, fill=white, thick] coordinates {(3,0)};
\end{axis}

\end{tikzpicture}