[рони]

<style type="text/css">
td.active + td:after{
    content: "нужная ячейка"
}

</style>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.2/css/bootstrap.min.css">
<script type="text/javascript" src="https://code.jquery.com/jquery-3.3.1.min.js"></script>
<div class="row">
<div class="col-2">
  </div>
<div class="col-9">
  <table class="table table-bordered table-hover  testTable table-sm">
    <thead>
       <tr class="bg-info text-white">
         <td>Ячейка 1</td>
           <td>Ячейка 2</td>
        </tr>
    </thead>
    <tbody>
        <tr>
           <td>тест</td>
           <td></td>
        </tr>
        <tr>
            <td>тест2</td>
            <td></td>
        </tr>
     </tbody>
   </table>
</div>
<script>
var tableTd;
$('.testTable').on('click', 'td', function () {
            $(this).addClass('active');
});


</script>