2 of 2 added 420 characters in body

Try bellow code

<?php

namespace Mainf\Stickers\Block;

class Discount extends \Magento\Framework\View\Element\Template
{
    protected $_product = null;

    protected $_registry;
    protected $_productFactory;

    /**
     * @param \Magento\Framework\View\Element\Template\Context $context
     * @param \Magento\Framework\Registry $registry
     * @param array $data
     */
    public function __construct(
        \Magento\Framework\View\Element\Template\Context $context,
        \Magento\Framework\Registry $registry,
        \Magento\Catalog\Model\ProductFactory $productFactory,
        array $data = []
    ) {
        $this->_registry = $registry;
        $this->_productFactory = $productFactory;
        parent::__construct($context, $data);
    }

    public function getCurrentCategory()
    {       
        return $this->_registry->registry('current_category');
    }

    public function getCurrentProduct()
    {       
        return $this->_registry->registry('current_product');
    }

    public function isDiscounted()
    {
        $idProd = $this->getCurrentProduct()->getData('entity_id');

        return true;
    }
}

Display current product data in your template (custom.phtml) file

if ($currentProduct = $block->getCurrentProduct()) {
    echo $currentProduct->getName() . '<br />';
    echo $currentProduct->getSku() . '<br />';
    echo $currentProduct->getId() . '<br />';       
}