Hard little lumps under my skin on both of my arms right before my elbows could it be cancer or swelling?

Many possibilities: There are many entities that could cause bumps under the skin. One course of action could be to see a dermatologist. They would be able to evaluate the lesions and determine whether biopsy is warranted.

Probably not: Cancer would not be the first thing that i would think of. However you should show these to your friendly dermatologist to find the cause.