<lightning:select  value="{!v.BatchInstance.LeadTime__c}" aura:Id="leadtimesel" onchange="{!c.validateotherleadtime}">
             <option value=""> - </option> 
             <option value="Within 48 hours"> Within 48 hours </option> 
             <option value="1 Week"> 1 Week </option> 
             <option value="2 Weeks"> 2 Weeks </option>
             <option value="3 Weeks"> 3 Weeks </option> 
             <option value="4 Weeks"> 4 Weeks </option> 
             <option value="5 Weeks"> 5 Weeks </option> 
             <option value="6 Weeks"> 6 Weeks </option> 
             <option value="7 Weeks"> 7 Weeks </option> 
             <option value="8 Weeks"> 8 Weeks </option> 
             <option value="More than 8 weeks"> More than 8 weeks </option> 
             <!--<option value="1 week if Qty<=999, 4 weeks if Qty>999"> 1 week if Qty<=999, 4 weeks if Qty>999 </option> 
             <option value="1 week if Qty<=249, 2 weeks if Qty>249"> 1 week if Qty<=249, 2 weeks if Qty>249 </option> -->
             <option value="In stock"> In stock </option> 
             <option value="Other"> Other </option> 
             </lightning:select>   
        </td>
         <td>
            <lightning:input  value="{!v.BatchInstance.Other_Lead_Time__c}" aura:id="otherleadtime" />
        </td>

 

validateotherleadtime : function(component, event, helper) {
    var leadesl = component.find("leadtimesel");
    var leadeslvalue = leadesl.get("v.value");  
    var otherleadtime = component.find("otherleadtime");
    var otherleadtimevalue = otherleadtime.get("v.value");  
    
      if(leadeslvalue==='Other' & !otherleadtimevalue) {
            otherleadtime.set("v.errors", [{message:"Other lead time is compulsory"}]);
        }else{
         //otherleadtime.set("v.errors", null);
        }
   }

I want to make other lead time value compulsory when they select lead time as "other" and I want to show this error, message on each and every step and action not at the end while clicking save button