I have been being watched for lymphoma, and have multiple enlarged lymph nodes. the left lower side has been hurting, could that be my spleen?

It is possible: Depending on how low, could be your spleen, intestines, kidney or even ovary. Given your enlarged lymph nodes, an enlarged spleen is definitely a possibility. As you may have been told, if lymphoma is a concern, a biopsy will be required to make the diagnosis. I hope you get better soon. Good luck.

Possible.: Spleen is basically a very large lymph node with specialized cells, and can enlarge along with the other lymphatic tissue. On the other hand, it's closer to the upper-left of the abdomen, and rarely hurts even when enlarged. You do need to see your doctor to sort this out.