Here is one try at it that gets the cell rectangle, and shrinks it a little, and then tests whether the point is in the shrunken rect.
private void gridControl1_MouseDown(object sender, MouseEventArgs e)
{
int row, col;
Point pt = new Point(e.X, e.Y);
if(this.gridControl1.PointToRowCol(pt, out row, out col, -1))
{
Rectangle rect = this.gridControl1.ViewLayout.RangeInfoToRectangle(GridRangeInfo.Cell(row, col),
true, GridCellSizeKind.ActualSize);
rect.Inflate(-3, -3);
if(rect.Contains(pt))
{
Console.WriteLine("Inside cell");
}
}
}