“Swollen lymph nodes under right armpit for more than 3 months?”

I took the first vaccination on the left arm and had no adverse side effects. Pfizer. However, about a month later I began having a burning sensation in my right armpit, not always, most days would be ok, but one or two days it would hurt. As I understand it this is due to a lymph blockage or that my body is fighting an infection, worse case cancer cells.

Of course, most doctors would assume the illness doesn't stem from the vaccine, but there have been reports of contralateral axilla lymphadenopathy reported in Pfizers documented medical trials. I feel it may be related to the vaccine as I have never had any issues such as this ever, could it really be a coincidence?

I am male, 45 y/o, not overweight, good fitness, and a clean eater. I have had an ultrasound, but am still waiting for my doctor to contact me regarding the results, the clinician who performed the scan, did inform me I have reactive lymph nodes. There are no noticeable lumps in this area to the touch.

My questions are:
1. What should be my best line of inquiry with my GP to get to the bottom of this issue, blood tests, more scans, would it be a good idea to go straight to a biopsy?
2. I have seen a lot of news lately about lymph system blockages, as I understand it this should only be a 2/3 week maximum period, but sometimes when it hurts, if I do some stretching or go for a run, the pain does in fact subside.
3. Are there any immediate things I could do to rule out the worse-case scenarios, such as blood cancers and other horrors?

Any other great information on this matter would be appreciated and thank you in advance for your time and expertise.