Without being able to dig too deep into an override (since you're in Architect) then you can create a container using hbox layout and have the field and a component where component is the icon.
I resolved... on the afterrender of the component I use this funcion:
function setToolTipInfo(cmp,msg,titolo){
var idInfo= cmp.id+'_info';
cmp.bodyEl.insertHtml('afterEnd','<span class="icon-info" id="'+idInfo+'"></span>');
setToolTip(idInfo,idInfo,msg,titolo);
}
function setToolTip(id,target,msg,titolo){
var myTootlip= Ext.getCmp('ToolTip'+id);