documentclass[border=2mm]{standalone}
usepackage{tikz}
begin{document}
    begin{tikzpicture}
    draw (0,0) circle (2cm);
    draw (0,0) circle (2.5cm);
    clip (0,0) circle (1.8cm);
    foreach i in {-2,-1.5,...,2} {
        foreach j in {-2,-1.5,...,2} {
            draw (i,j) circle (0.2cm);
        }
    }
    end{tikzpicture}
end{document}