2y old f I noticed a pea size lump bk of rt ear 2 dr felt and said normal but why would I feel on one side and not the other s?

Variation. One side may have a lipoma, a harmless fatty mass or a more prominent lymph node . It could also be a boney prominence that is larger on one side. Symmetry in the body is not perfect.
Lymph node. Not uncommon to have a swelling of the lymph nodes on one side of the body and not the other. As long as there is no other infection associated with the lymph node, time and observation is the best course.