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 />';       
    }