From the symptoms it looks like allergic reaction to the jelly fish bite but from the symptom of swollen lymph nodes, the possibility of any superimposed bacterial infection or cellulitis needs to be ruled out. It usually follows a break in the skin, such as a fissure, cut, laceration, insect bite, or puncture wound.
Blood culture sensitivity is often done to find out the causative pathogen and its sensitivity to various antibiotics. If it is MRSA, then antibiotics other than amoxycillin can be prescribed depending upon the blood culture report.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Thanks for your help, Dr. Bhupinder. It must have been an allergic reaction, as it went away on its own over the course of two weeks. If there was any additional infection, my body fought it off without medication. Thanks again for taking the time to address my problem, I truly appreciate it!