is it possible for someone else to block your heart with a curse?
Neither physically nor spiritually. The only impact others, including Satan, can have is to suggest ideas to you, that your understanding then will consider. It can be either a visual image or words. These can also incite your own emotions or appetites to either want what is suggested or be afraid of what is suggested or be sad about what is suggested. Then your emotions or appetites turn back to your reason with desire to be satisfied (for what seems appealing) or desire to end the fear or desire to end the sadness.
Your emotions or appetites are asking your reason to figure out answers to accomplish these. But your reason can also choose to ignore your emotions or appetites when they are about incorrect or wrong desires or fears or sorrows.
When someone curses you, you can remember who you belong to, your Lord Jesus. You can remember that he gave you participation in himself, his body and blood, when you last received communion at Mass. And then you can choose that you will honor Him by believing His blessing of you and feeding of you, giving you an open heart. And then you can say, the one cursing does not know what they are talking about.