When I eat something slighty hard or tough, my gums gets itchy and irritated like I just need to rub them hard with my fingers. There's no bleeding or swelling. What could this be and what's the treatment?

Allergy/Irritation. It is difficult to say. You may have a slight allergy to certain foods or just like you stated in your question it could be that the toughness of the food is irritating. Sometimes you can make your tissues more sensitive when you switch brands of toothpaste or mouthwash. I would look at that first if you recently switched.