Lower back pains when i run on uneven surface and recently felt a small lump on my lower right back?

Needs examination : Might be a muscle spasm but there are other possibilities that require a physical examination to sort out. Best see a doctor

More info needed: Given your age, this is very likely a non-sinister cause like a muscular injury or strain. However, as others have said, you need to be examined + go through the history in much more detail to be sure. A physiotherapist or a GP are both good places to start.

Usually benign: Typically that lump in your lower back is an area in the thoracolumbar fascia that develops a know. It is not typically dangerous and becomes "inflamed" and painful when aggravated. For you it sounds like that factor is running on uneven surfaces. Keep on eye on it. See if smooth surface running doesn't cause the pain. If it increases in size or pain persists; see a specialist. Hope that helps!