A lump of something is a solid piece of it.

A lump on or in someone's body is a small, hard swelling that has been caused by an injury or an illness.

A lump of sugar is a small cube of it.

If you say that someone will have to lump it, you mean that they must accept a situation or decision whether they like it or not.

If you say that you have a lump in your throat, you mean that you have a tight feeling in your throat because of a strong emotion such as sorrow or gratitude.